Stem Cells for Mesothelial Repair: An Understudied Modality

Adhesions are bands of fibrous tissue that form between opposing organs and the peritoneum, restricting vital intrapleural and abdominal movement. They remain a major problem in abdominal surgery, occurring in more than three fourths of patients following laparotomy. Adhesions result when injury to the mesothelium is not repaired by mesothelial cells and can be viewed as scar tissue formation. The mechanism of mesothelial healing suggested the involvement of stem cells in the process. It has long been known that peritoneal wounds heal in the same amount of time regardless of size. Therefore, the mesothelium could not regenerate solely by proliferation and centripetal migration of cells at the wound edge as occurs in the healing of skin epithelium. Several studies suggest the presence of i) mesothelial stem cells that can differentiate into mesothelial cells and a few other phenotypes and/or ii) that mesothelial cells are themselves stem cells. Other studies have suggested that adult stem cells in the muscle underlying the peritoneum can differentiate into mesothelial cells and contribute to healing. Prevention of abdominal adhesions have been accomplished by delivery of autologous mesothelial cells and multipotent adult stem cells isolated from skeletal muscle. Adult stem cells from sources other than the serosal tissue offer an alternative treatment modality to prevent the formation of abdominal adhesions.

The impact of genital trauma on wounded servicemen: qualitative study

BACKGROUND

Recent military operations in Afghanistan have resulted in considerable lower limb trauma. Associated with this trauma have been serious injuries to the genitalia. No previous study has looked at the effect of traumatic genital injury on the individual. This study expresses the impact of these injuries.

METHODS

A qualitative evaluation, interviewing 13 male patients with extensive genital injuries, including 11 patients with orchidectomies.

RESULTS

Patients attach a very high importance to their genital injury, rating this injury as having more impact than lower limb amputations. They also have a high expectation for the recovery of sexual function. Psychological outcomes are better when an individual's future fertility is known at an early stage.

CONCLUSION

Better outcomes are achieved for the patient when psychological and surgical support if provided throughout the long treatment and recovery process It is important that every effort is made to preserve fertility right from the point of injury.

A population of cells resident within embryonic and newborn rat skeletal muscle is capable of differentiating into multiple mesodermal phenotypes

We have previously shown a population of putative mesenchymal stem cells in the connective tissue surrounding embryonic avian skeletal muscle. These cells differentiate into at least five recognizable phenotypes in culture: fibroblasts, chondrocytes, myotubes, osteoblasts, and adipocytes. We have now isolated a similar population of cells from fetal and newborn rat skeletal muscle. Cells from rat leg muscle were dissected, minced, and then enzymatically digested with a collagenase-dispase solution. The dissociated cells were plated and allowed to differentiate into two recognizable populations: myotubes and stellate mononucleated cells. The cells were then trypsinized, filtered through a 20 microm filter to remove the myotubes, frozen at -80 degrees C, then thawed and replated. In culture the cells maintained their stellate structure. However, under treatment with dexamethasone, a nonspecific differentiating agent, seven morphologic conditions emerged: cells with refractile vesicles that stained with Sudan black B (adipocytes), multinucleated cells that spontaneously contracted in culture and stained with an antibody to myosin (myotubes), round cells whose extracellular matrix stained with Alcian blue, pH 1.0 (chondrocytes), polygonal cells whose extracellular matrix stained with Von Kossa's stain (osteoblasts), cells with filaments that stained with an antibody to smooth muscle a-actin (smooth muscle cells), cells that incorporated acetylated low density lipoprotein (endothelial cells), and spindle-shaped cells that grew in a swirl pattern (fibroblasts). The initial population is tentatively classified as putative mesenchymal stem cells. The presence of these cells point to the existence of stem cells in the postembryonic mammal that could provide a basis for tissue regeneration as opposed to scar tissue formation during wound healing.

Human reserve pluripotent mesenchymal stem cells are present in the connective tissues of skeletal muscle and dermis derived from fetal, adult, and geriatric donors

This study details the profile of 13 cell surface cluster differentiation markers on human reserve stem cells derived from connective tissues. Stem cells were isolated from the connective tissues of dermis and skeletal muscle derived from fetal, mature, and geriatric humans. An insulin/dexamethasone phenotypic bioassay was used to determine the identity of the stem cells from each population. All populations contained lineage-committed myogenic, adipogenic, chondrogenic, and osteogenic progenitor stem cells as well as lineage-uncommitted pluripotent stem cells capable of forming muscle, adipocytes, cartilage, bone, fibroblasts, and endothelial cells. Flow cytometric analysis of adult stem cell populations revealed positive staining for CD34 and CD90 and negative staining for CD3, CD4, CD8, CD11c, CD33, CD36, CD38, CD45, CD117, Glycophorin-A, and HLA DR-II.

Muscle morphogenetic protein induces myogenic gene expression in Swiss-3T3 cells

Myogenesis is thought to be regulated by the MyoD family of regulatory genes, which includes MyoD, myogenin, MRF- 4/myf-6, and myf-5. In situ hybridization studies of vertebrate skeletal muscle development have shown the colocalization of the MyoD family of regulatory genes to specific stages of muscle development. Although many studies have analyzed the regulatory role of these genes during myogenesis, there have been few reports dealing with the activation of these myogenic regulatory genes by exogenous agents. We have previously shown that muscle morphogenetic protein induces myogenesis in clonal populations of avian pluripotent stem cells. The current study was designed to examine the ability of muscle morphogenetic protein to induce myogenesis in a clonal population derived from the established fibroblastic Swiss-3T3 cell line. Swiss-3T3 cells were cloned to generate separate cell populations, tested for pluripotency, propagated through 690 cell doublings, retested for pluripotency, treated with muscle morphogenetic protein, and examined for the induction of gene expression using probes for the transcription products of MyoD and myogenin. Muscle morphogenetic protein induced the expression of mRNAs for MyoD and myogenin, suggesting a role for this compound as an exogenous activator of myogenesis.

Bioactive factors affect proliferation and phenotypic expression in progenitor and pluripotent stem cells

Progenitor and pluripotent stem cells reside within connective tissue compartments. They are also present in granulation tissue. This study examined the effects of treating these two cell populations with eight bioactive factors. Cells were assayed for DNA content as a measure of proliferation and for tissue-specific phenotypic markers as measures of lineage progression and lineage commitment. Platelet-derived endothelial growth factor and insulin-like growth factor-II did not induce proliferation in either population. However, dexamethasone, insulin, insulin-like growth factor-I, muscle morphogenetic protein, platelet-derived growth factor-AA, and platelet-derived growth factor-BB stimulated proliferation in one or both cell populations. Platelet-derived growth factor-BB was the most potent stimulator of proliferation in either population. Phenotypic expression markers were induced in the progenitor cells by insulin, insulin-like growth factor-I, insulin-like growth factor-II, dexamethasone, and muscle morphogenetic protein. However, only dexamethasone and muscle morphogenetic protein induced phenotypic expression markers in the pluripotent cells. Platelet-derived endothelial cell growth factor, platelet-derived growth factor-AA, and platelet-derived growth factor-BB did not induce phenotypic expression markers in progenitor or pluripotent cells. This study suggests the potential for using progenitor and pluripotent cells as an in vitro model to ascertain the effects of various bioactive factors on stem cells potentially involved in tissue maintenance and repair.

Interrogative suggestibility in patients with conversion disorders

We tested the hypothesis that increased interrogative suggestibility may contribute to the shaping and maintaining of conversions symptoms. Interrogative suggestibility was measured in 12 patients with conversion disorder and 10 control patients with confirmed neurological disease matched for age, premorbid intelligence, and as closely as possible in terms of their neurological symptoms to the patients with conversion disorder. Our observations do not support the contention that individual differences in interrogative suggestibility are of importance in the etiology of conversion disorders.

Formation of abdominal adhesions is inhibited by antibodies to transforming growth factor-beta1

Transforming growth factor-beta (TGF-beta) is an important factor in regulating the inflammatory response and the production of extracellular matrix by fibroblasts. These two processes are linked in the formation of fibrous adhesions after abdominal surgery. When the mesothelium is injured a fibrin strand is produced which is populated first by inflammatory cells then by fibroblasts which secrete extracellular matrix forming a permanent adhesion. TGF-beta promotes both chemotaxis of monocytes and the production of extracellular matrix by fibroblasts. We have used a model of abdominal adhesions in rats in which a circle of peritoneum is dissected and then sutured into place again. After 2 weeks the rats are euthanized and the adhesions are scored. Six groups of 10 rats each underwent this surgery. Group I served as the operative control. Group II was treated with saline which was injected immediately after surgery and on Days 1 and 2 after surgery (vehicle control). Using the same protocol with saline as vehicle, the other four groups of rats were treated with nonspecific IgG (150 microgram per day), anti-TGF-beta (panspecific, 167 microgram per day), anti-TGF-beta1 (67 microgram per day), or anti-TGF-beta2 (50 microgram per day). The rats injected with anti-TGF-beta1 had significantly lower adhesion scores (P < 0.05) than the controls. Rats injected with anti-TGF-beta2 or anti-TGF-beta (panspecific) did not differ significantly from the control saline-injected rats. The results indicate that specifically reducing levels of TGF-beta1 alone can be effective in preventing abdominal adhesions.

Recombinant human bone morphogenetic proteins-2 and -4 induce several mesenchymal phenotypes in culture

Bone morphogenetic protein has previously been shown to induce the formation of cartilage and bone in vivo. We have isolated a population of mesenchymal stem cells from rat skeletal muscle capable of forming multiple mesodermal morphologies in vitro. These cells were treated with recombinant human bone morphogenetic proteins-2 and -4 to determine the differentiation-inducing activities of bone morphogenetic protein on these cells. The mesenchymal stem cells were cultured in medium with 10% preselected horse serum containing 0 to 100 ng/ml recombinant human bone morphogenetic proteins-2 or -4 for a maximum of 4 weeks. Control cultures maintained the stellate morphology of mesenchymal stem cells. Cultures treated with recombinant human bone morphogenetic protein-2 exhibited discrete cartilage nodules and mineralized bone nodules. The first increase in chondrogenesis was seen at 0.5 ng/ml. Cultures treated with recombinant human bone morphogenetic protein-4 also exhibited an increase in chondrogenesis at the higher concentration of 2 ng/ml. Skeletal myotubes and adipocytes also appeared in cultures treated with either bone morphogenetic protein. Mesenchymal stem cells do respond to inductive factors, but bone morphogenetic proteins-2 and -4 were not specific for the induction of cartilage and bone.

Effect of rat mesenchymal stem cells on development of abdominal adhesions after surgery

One of the common and most serious side effects of abdominal surgery is the formation of adhesions within the peritoneal cavity during healing. Efforts to prevent adhesion formation have concentrated on inhibiting the inflammatory response, inhibiting the formation or encouraging the lysis of fibrin, and protection of the damaged serosal surface. We are interested in regenerating the serosal surface by providing a source of mesothelial progenitor cells. Rats were divided into groups of 10 each. Abdominal adhesions were created by removing a circle of peritoneum and suturing it back into place. Two weeks later the rats were euthanized and the adhesions scored on a scale of 0-5. A population of mesenchymal stem cells (MSCs) isolated from the skeletal muscle of neonatal rats was tested. The cells were grown in primary culture to expand the population and then trypsinized and frozen at -80 degrees C. They are then thawed and grown in secondary culture before use. The control group were injected with saline i.p. immediately after surgery. The experimental groups received (1) 1.4 X 10(6) MSCs, (2) 5 X 10(6) MSCs, (3) 7.5 X 10(6) dead MSCs, (4) 5 X 10(6) rat smooth muscle cells immediately post-op, and (5) 5 X 10(6) MSCs 4-6 hours after surgery. Only live MSCs given immediately after surgery by i.p. injection significantly decreased the adhesion scores of the rats (mean score of 3.5 vs 0.9). MSCs injected i.p. 4-6 hours after surgery actually increased the adhesion scores (3.5 vs 4.7), and rat smooth muscle cells injected i.p. immediately after surgery had no effect on adhesions. The exact mechanism of action of the MSCs is unknown at this time. However, we postulate that the MSCs have the capacity to differentiate into mesothelial cells capable of repopulating the injured mesothelium.

A population of cells isolated from rat heart capable of differentiating into several mesodermal phenotypes

A population of stem cells has been isolated from embryonic avian and neonatal rat skeletal muscle. These cells differentiate into several mesodermal phenotypes in culture upon treatment with dexamethasone. This study reports the isolation of a similar population of stem cells from another mesodermal tissue, the heart. Hearts were excised from 3- to 5-day- old rats, minced, and treated with a collagenase-dispase solution. Single cells were collected by centrifugation, washed, and plated in dishes. The cells were grown to confluence, trypsinized, and frozen at -80 degrees C in 7.5% dimethylsulfoxide. After at least 24 hr, the cells were thawed and plated in 24-well plates and treated with media containing dexamethasone at concentrations of 10(-6)-10(-10) M for 4 weeks. Control cultures contained mononucleated cells with a stellate morphology. Treatment with dexamethasone resulted in the appearance of several mesodermal phenotypes. Bone and cartilage nodules were identified with von Kossa and Alcian blue staining respectively. Adipocytes were identified using Sudan black B stain. Smooth muscle cells were identified by an anti-smooth muscle alpha-actin antibody, and skeletal myotubes were stained with anti-myosin antibody. Large binuclear cells with obvious fibers were noted and stained with anti-desmin. These binuclear cells appeared in both the control and the dexamethasone-treated cultures and were tentatively identified as cardiomyocytes. These data strongly suggest the existence of a population of mesenchymal stem cells in neonatal rat heart.

Loin pain and haematuria syndrome: a somatoform disorder

Fifteen patients with the loin pain and haematuria syndrome (LPH) were compared with 10 patients with complicated renal stone disease referred to the same tertiary centre and matched for age, sex and duration of illness. LPH patients had a history of three times more medically unexplained somatic symptoms other than loin pain (p < 0.01) and a higher proportion took analgesics regularly (p < 0.01). The onset of pain was associated with an adverse psychologically important life-event in eight of the LPH patients but in none of the controls (p < 0.02). LPH patients more frequently recalled serious parental illness and disability in childhood (p < 0.001) than controls, and a higher proportion felt responsible for causing or alleviating parental illness or distress (p < 0.05). LPH subjects scored higher in the 'paternal care' dimension of the Parental Bonding Instrument (p < 0.05). No difference was found between LPH patients and controls in terms of current depression and anxiety but both groups exhibited high rates of lifetime depression. LPH patients expressed lower levels of anger and hostility (p < 0.002) than did controls. Our observations suggest that psychological factors are of major importance in the aetiology of LPH, which may represent a type of somatoform pain disorder.

Differentiation factors induce expression of muscle, fat, cartilage, and bone in a clone of mouse pluripotent mesenchymal stem cells

Growth factors have been used experimentally to accelerate wound healing by increasing scar tissue formation at a wound site. These studies suggest that stimulation of fibroblastic differentiation and proliferation are essential components of adult tissue repair. Recent studies report the presence of mesenchymal stem cells within granulation tissue and as connective tissue-resident stem cells. This suggests that mesenchymal stem cells as well as fibroblasts may contribute to wound healing and repair. To determine the potential for mesenchymal stem cells to contribute to nonfibrogenic tissue repair, a clonal population of murine mesenchymal stem cells was examined with dexamethasone, a general differentiation agent, and muscle morphogenetic protein, a specific differentiation-inducing agent. Dexamethasone induced the expression of phenotypic markers for fat, cartilage, and bone in the stem cells. Muscle morphogenetic protein induced the expression of mRNAs for the muscle specific regulatory genes MyoD1 and myogenin in these cells. These results suggest that pluripotent mesenchymal stem cells within connective tissue compartments and granulation tissue have the potential to contribute to functional tissue restoration, rather than contributing solely to fibrogenic scar tissue formation during tissue repair.

Inhibition of epidural scar formation after lumbar laminectomy in the rat

STUDY DESIGN

An animal model of laminectomy in rats was used to study scar tissue formation around the spinal cord. Dexamethasone, in controlled-release form, was tested in this system for its ability to decrease fibrous tissue formation.

OBJECTIVES

The results were evaluated to determine whether dexamethasone in a biodegradable controlled-release vehicle could be used to limit scar tissue formation around the spinal cord after laminectomy.

SUMMARY OF BACKGROUND DATA

Steroids can delay the formation of scar tissue. Continued treatment with dexamethasone results in various unacceptable side effects. Use of biodegradable controlled-release vehicles to deliver drugs may allow for prolonged low-dose treatment, concentrated at the surgical site, thereby avoiding side effects.

METHODS

Forty-four Sprague Dawley rats underwent laminectomies and were treated with dexamethasone in one of two controlled-release vehicles or with vehicle alone. After 4 weeks, the rats were killed and histologic sections prepared from the spines were examined and graded by a pathologist. In addition, the dexamethasone preparations were introduced into Hunt-Schilling wound chambers, which were implanted in rats. Four weeks after implantation, the wound chambers were removed and the tissue inside was assayed for DNA and protein content.

RESULTS

Dexamethasone acetate (Decadron, MSD, West Point, PA) significantly reduced the density of the scar tissue undermining the laminas. Steroids embedded in polymer did not change the scar formation in the back, but did decrease protein and DNA values in wound chamber tissues.

CONCLUSIONS

Long-term release of small amounts of steroid from the polymer poly-carboxy-phenoxypropane does not appear to reduce scar at laminectomy sites but does decrease the protein:DNA ratio in wound chambers. In contrast, Decadron does not significantly alter the biochemistry of wound chamber tissue but does reduce scar in the back.

Mesenchymal stem cells reside within the connective tissues of many organs

Previous studies have noted the presence of mesenchymal stem cells located within the connective tissue matrices of avian skeletal muscle, dermis, and heart. In these studies, clonal analysis coupled with dexamethasone treatment revealed the presence of multiple populations of stem cells composed of both lineage-committed progenitor mesenchymal stem cells and lineage-uncommitted pluripotent mesenchymal stem cells. The present study was undertaken to assess the distribution of these stem cells in the connective tissues throughout various regions of the body. Day 11 chick embryos were divided into 26 separate regions. Heart, limb skeletal muscle, and limb dermis were included as control tissues. Cells were harvested enzymatically and grown using conditions optimal for the isolation, cryopreservation, and propagation of avian mesenchymal stem cells. Cell aliquots were plated, incubated with various concentrations of dexamethasone, and examined for differentiated phenotypes. Four recurring phenotypes appeared in dexamethasone-treated stem cells: skeletal muscle myotubes, fat cells, cartilage nodules, and bone nodules. These results suggest that progenitor mesenchymal stem cells and putative pluripotent mesenchymal stem cells with the potential to form at least four tissues of mesodermal origin have a widespread distribution throughout the body, being located within the connective tissue compartments of many organs and organ systems.

Auditory-verbal hallucinations and the phonological loop: a cognitive neuropsychological study

A patient with continuous auditory-verbal hallucinations was studied, in comparison with two cases with a past history of similar hallucinations, from a cognitive neuropsychological perspective. This attempts to place hallucinations in the context of a normal cognitive process which has become disordered. The process in question is the phonological loop, equivalent to inner speech, derived from a model of short-term or working memory. A series of short-term memory tests, assumed to rely on the adequate functioning of the phonological loop, was administered, the results of which broadly conformed to a normal pattern of performance. It is concluded that verbal hallucinations cannot be regarded as involving the phonological loop directly. Other points in the short-term memory/language system at which verbal hallucinations could arise are discussed, as are suggestions for further research of this kind.

Pluripotent mesenchymal stem cells reside within avian connective tissue matrices

Recent studies have noted the presence of putative stem cells derived from the connective tissues associated with skeletal muscle, heart, and dermis. Long-term continuous cultures of these cells from each tissue demonstrated five distinct phenotypes of mesodermal origin, i.e. muscle, fat, cartilage, bone, and connective tissue. Clonal analysis was performed to determine whether these morphologies were the result of a mixed population of lineage-committed stem cells or the differentiation of pluripotent stem cells or both. Putative stem cells from four tissues (skeletal muscle, dermis, atria, and ventricle) were isolated and cloned. Combined, 1158 clones were generated from the initial cloning and two subsequent subclonings. Plating efficiency approximated 5.8%. Approximately 70% of the 1158 clones displayed a pure stellate morphology, while the remaining clones contained a mixture of stellate, chondrogenic- or osteogenic-like morphologies or both. When cultured in the presence of dexamethasone, cells from all clones differentiated in a time- and concentration-dependent manner into muscle, fat, cartilage, and bone. These results suggest that pluripotent mesenchymal stem cells are present within the connective tissues of skeletal muscle, dermis, and heart and may prove useful for studies concerning the regulation of stem cell differentiation, wound healing, and tissue restoration, replacement and repair.

Epithelial abnormalities in intestine and kidney of the spontaneously hypertensive rat

A variety of perturbations of calcium metabolism are reported to occur in the spontaneously hypertensive rat (SHR) compared to its genetic control the Wistar-Kyoto rat (WKY), including significant dysfunction of calcium handling by the proximal renal tubule of the SHR, resulting in impaired active calcium transport in the gut and an apparent renal calcium leak. We explored the intestinal and renal epithelia of 12- to 14-week-old SHR and WKY using electron microscopy. Biochemical comparisons of these transport epithelia included measurements of three vitamin D dependent cellular proteins and one structural protein: alkaline phosphatase, intestinal CaBP9K, renal CaBP28K, and villin expression. Electron microscopy demonstrated a patchy loss in microvilli in the SHR, accounting for approximately 10 to 15% of the total microvillar surface. In the kidney, morphological abnormalities were observed only in the proximal renal tubule. Again, there was patchy loss of microvilli from the brush border membrane. In SHR duodenal alkaline phosphatase activity was significantly reduced compared to the WKY (0.145 +/- 0.002 v 0.186 +/- 0.002 integrated extinction/min/micron 3 X 10(3) brush border (P less than .001). Duodenal CaBP9K and renal CaBP28K were significantly reduced in SHR compared to WKY. There were no differences in villin expression. These data are consistent with the previously characterized disturbances of active calcium transport in the intestine and inappropriate renal calcium leak in the SHR. While a possible link between these disturbances and hypertension remains to be determined, this study provides supportive evidence for a primary disturbance in cell calcium handling and transporting epithelia in this form of genetic hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Ectopic induction of cartilage and bone by water-soluble proteins from bovine bone using a polyanhydride delivery vehicle

Controlled release delivery vehicles for water-soluble osteogenic proteins from demineralized bovine bone matrix were constructed using polyanhydride polymers. The water-soluble proteins were isolated from a 4 M guanidine hydrochloride extract of bone matrix. The water-soluble proteins possessed Chondrogenic Stimulating Activity (CSA) when tested in stage 24 chick limb bud cell cultures, but were incapable of inducing cartilage or bone in vivo when implanted intramuscularly into mice by themselves. The polyanhydride polymers alone were also incapable of inducing ectopic cartilage or bone. However, when the water-soluble proteins were incorporated into the polymeric delivery vehicle, the combination was capable of inducing cartilage and bone up to 50% of the time. These results demonstrate that it is possible to use polyanhydride polymers as controlled-release delivery vehicles for soluble bioactive factors that interact with a local cell population.

Ultrastructural and functional abnormalities of intestinal and renal epithelium in the SHR

Intestinal calcium transport, renal tubular calcium reabsorption, and plasma 1.25 (OH)2 vitamin D3 (calcitriol) levels have all been reported to be diminished in the spontaneously hypertensive rat (SHR) compared with its genetic control the Wistar Kyoto rat (WKY). In the present study, absorptive duodenal and renal tubular epithelia of 12- to 14-week-old male SHR and WKY were examined by electron microscopy to determine whether such disturbances could be related to structural abnormalities. Patchy loss of microvilli in both duodenal and proximal tubular epithelia was observed in the SHR, whereas brush border membrane was entirely normal in the WKY. Irregular spaces were observed between the basal aspects of SHR intestinal epithelial cells and their basement membrane. In addition, the average height of duodenal and renal microvilli was reduced in the SHR. Two specific markers of the brush border membrane, alkaline phosphatase and villin, as well as the cytoplasmic vitamin-D dependent calcium-binding proteins, CaBP9K and CaBP28K were determined. Duodenal alkaline phosphatase activity was reduced in the SHR, compared with the WKY: 0.145 +/- 0.002 vs. 0.186 +/- 0.002 IE/min.microns 3 x 10(3) brush border, mean +/- SEM, N = 10 pairs, P less than 0.001. However, duodenal villin expression was not different from that of the WKY. Duodenal CaBP9K and renal CaBP28K content was diminished in the SHR: 21.0 +/- 0.80 vs. 29.9 +/- 2.19 micrograms/mg protein, N = 6 pairs, P less than 0.01 for duodenum, and 4.47 +/- 0.39 vs. 7.67 +/- 0.54 micrograms/mg protein, N = 6 pairs, P less than 0.001 for kidney. These data showing structural and functional abnormalities of intestinal and kidney cells in the SHR appear to reflect a disorder of transporting epithelia which may be either intrinsic or related to reduced circulating calcitriol.

Bone marrow fat content in relation to bone remodeling and serum chemistry in intact and ovariectomized dogs

It was previously shown that 11 months after ovariectomy the volume fraction of trabecular bone in the spine and 11th rib medullary canal of Beagle dogs (6 control, 9 ovariectomized) was significantly reduced. In this paper it is shown that these changes are accompanied by increased marrow fat volume in the 11th rib (59.0 +/- 9.5% vs. 44.3 +/- 10.0%). Conversely, the volume fraction of functional (hematopoietic) cells in the marrow was reduced by ovariectomy. Additionally, variations in marrow fat volume were tested for correlation with 22 other variables pertinent to bone physiology. Marrow fat volume was significantly positively correlated with serum osteocalcin, rib trabecular bone porosity, rib cross-sectional area, and gains in body weight. It was negatively correlated with serum estrogen concentrations and the extent of rib trabecular surfaces labeled with tetracycline.

Ectopic induction of cartilage and bone by water-soluble proteins from bovine bone using a collagenous delivery vehicle

A controlled-release delivery vehicle for water-soluble osteogenic proteins from demineralized bone matrix was constructed using purified type I collagen. The water-soluble proteins were isolated from a 4 M GdnHCl extract of bone matrix. Although the water-soluble proteins were capable of inducing cartilage formation in vitro, they were incapable of inducing cartilage or bone in vivo when implanted intramuscularly into mice in the absence of an appropriate delivery vehicle. The collagen-based delivery vehicle alone was also incapable of inducing osteogenesis in vivo. However, when the water-soluble proteins were incorporated into the delivery vehicle, the combination was capable of inducing cartilage and bone 76% of the time. These results demonstrate that it is possible to formulate a controlled-release delivery vehicles for soluble bioactive factors which upon release interact with local responsive cells.

Hyperparathyroidism and abnormal calcitriol metabolism in the spontaneously hypertensive rat

Abnormalities of calcium metabolism and of its two principal regulating hormones, parathyroid hormone and 1,25-dihydroxyvitamin D3 (calcitriol), have been reported in the spontaneously hypertensive rat (SHR). Reports of abnormal calcitriol metabolism in the SHR by several groups have not provided measurements of tissue calcitriol receptors. Similarly, few data are available as to the parathyroid status of the SHR. In the present study, circulating calcitriol levels and intestinal and parathyroid gland calcitriol receptor status were determined in male SHR and in Wistar-Kyoto (WKY) rats. Parathyroid status was investigated by determination of parathyroid gland mass together with tissue micromorphometry and by quantitative histology of bone as a measure of the biological action of parathyroid hormone. Circulating calcitriol levels were reduced in the 11-week-old SHR compared with the WKY rat (165 +/- 23 vs. 194 +/- 28 pmol/l, p less than 0.01, mean +/- SD). Calcitriol-free ratio was diminished and maximal specific binding capacity for calcitriol was increased in the SHR in parathyroid tissue (172 +/- 4.9 vs. 123 +/- 6.6 fmol/mg protein, p less than 0.01) and in intestinal mucosa with no change of receptor affinity. Plasma ionized calcium (1.29 +/- 0.05 vs. 1.45 +/- 0.35 mmol/l, p less than 0.05) and phosphate (1.5 +/- 0.26 vs. 2.4 +/- 0.03 mmol/l, p less than 0.05) were significantly lower in the SHR. Parathyroid gland mass was increased in the SHR (59 +/- 12 vs. 17 +/- 7 micrograms/100 g body wt, p less than 0.001) as a result of hyperplasia and not hypertrophy. Higher osteoclast numbers were observed in SHR bone (27.6 +/- 0.79 vs. 23.9 +/- 0.66 osteoclasts/mm2, p less than 0.01), suggesting increased parathyroid hormone activity. In summary, in the 11-week-old SHR we observed reduced circulating calcitriol levels together with increased tissue calcitriol receptor numbers, increased parathyroid gland mass, and histological evidence of hyperparathyroidism. It is possible that these abnormalities influence the development of hypertension in the SHR.

Rapid stimulation of calcium uptake by isolated rat enterocytes by 1,25(OH)2D3

Evidence is accumulating that 1,25(OH)2D3 may stimulate calcium transport from the intestinal lumen extremely rapidly by a mechanism which appears independent of de novo protein synthesis. To investigate this rapid action of 1,25(OH)2D3, the rate of calcium uptake by isolated enterocytes from duodena of young rats was determined in vitro as the uptake of 45Ca from 1-15 min. Prior in vitro exposure of cells to 1,25(OH)2D3 (100 pM) for 20 min significantly increased the rate of calcium uptake (p less than 0.001), an effect unaltered by 50 microM cycloheximide. Incubation with 100 pM 1-alpha-hydroxyvitamin D3 produced the same effect (p less than 0.01). In contrast, exposure to 10 pM 1,25(OH)2D3, as well as to 100 pM or to 1,000 pM 25-hydroxyvitamin D3 induced no significant change. Because both 1,25(OH)2D3 and starvation may stimulate key enzymes in polyamine metabolism, we investigated the effects of (i) difluoromethyl-ornithine (CHF2-Orn), a specific irreversible inhibitor of ornithine decarboxylase and (ii) varying the timing of feeding prior to sacrifice. Both in vitro CHF2-Orn and feeding prior to sacrifice significantly decreased the baseline rate of calcium uptake (p less than 0.05) and reduced the effect of 1,25(OH)2D3. Increased duration of starvation significantly increased the baseline rate of calcium uptake (p less than 0.02) without changing the increment in rate of calcium uptake induced by 1,25(OH)2D3. The study suggests (i) that the early action of 1,25(OH)2D3 on the influx process of intestinal calcium transport may involve a different molecular specificity from that involved in the genomic action of 1,25(OH)2D3 and (ii) that changes in polyamine metabolism may play a part in this process.

Decreased duodenal enterocyte calcium flux rates in the spontaneously hypertensive rat

We have previously reported serum 1,25(OH)2 vitamin D3 (calcitriol) and active transduodenal calcium absorption measured in the Ussing chamber to be reduced in 12- to 14-week-old male Okamoto-Aoki spontaneously hypertensive rats (SHR). In the present study, we compared rates of calcium influx and efflux in isolated duodenal enterocytes in SHR and corresponding controls, Wistar-Kyoto rats (WKY). The early (0 to 1 minute) and the late (1 to 15 minute) phase of calcium influx rates at 1.0 mmol Ca2+ in the incubation medium were lower in the SHR than in the WKY (mean +/- SEM): 1.93 +/- 0.22 v 2.85 +/- 0.41 nmol/mg protein/min, n = 8 and n = 7 experiments, respectively, P less than .05; and 0.334 +/- 0.025 v 0.488 +/- 0.059 nmol/mg protein/min, n = 14 pairs, P less than .01. The calcium efflux rate constant of the SHR was reduced: 34.3 +/- 1.4 v 51.9 +/- 1.4% per hour, n = 11 pairs, P less than .01. However, in the absence of sodium or the presence of ouabain (4.0 mmol) in the incubation medium, a decrease in this constant was observed in the WKY but not in the SHR. These data, at the cellular level, support our previous observation in intact tissue of reduced active transduodenal calcium transport in the 12- to 14-week-old SHR. Whether the primary defect in calcium transport involves the luminal or the basolateral membrane of the enterocyte, or whether both disturbances are due to a common primary perturbation cannot be deduced from the present experiments.

Chemotactic response of osteoblast-like cells to transforming growth factor beta

Transforming growth factor beta (TGF-beta) was tested for its ability to stimulate a chemotactic response in two clonal rat osteosarcoma (ROS) cell lines, 17/2 and 25/1. TGF-beta stimulated dose-dependent chemotaxis in both cell lines. In serum-containing media, maximal response was seen at a concentration of 500 fg (10(-15)g)/mL for the ROS 17/2 cells and 25 fg/mL for the ROS 25/1 cells. In serum-free media, the maximal chemotactic response to TGF-beta occurred at 5 fg/mL for both the ROS 17/2 and 25/1 cells. TGF-beta was not mitogenic at these dosages. The results indicate that TGF-beta could act as a chemoattractant for osteogenic cells in both demineralized bone matrix induced osteogenesis and in normal bone remodeling.

Rapid (10-minute) stimulation of rat duodenal alkaline phosphatase activity by 1,25-dihydroxyvitamin D3

Recent reports have suggested that the action of calcitriol is much more rapid than previously thought. It is thus possible that some actions do not depend on de novo protein synthesis. A precise microdensitometric technique has been used to characterize the time course of the intestinal brush border alkaline phosphatase (AP) response of rat duodenal villi to the administration of calcitriol as AP activity has been shown to be dependent on the vitamin D status of the animal. The technique enables AP activity to be determined in situ without tissue disruption. After ip administration of 200 ng calcitriol to vitamin D-deficient male Wistar AF rats, a biphasic AP response was observed with an early peak within 1 h (0.068 +/- 0.011 vs. 0.101 +/- 0.003 integrated extinction (IE) min.micron 3 X 10(3), P less than 0.05) and a second at between 6 and 8 h (0.088 +/- 0.005 vs. 0.172 +/- 0.003 IE/min.micron 3 X 10(3), P less than 0.001). In a further experiment, the early response to calcitriol was reexamined with observations at 0, 10, 30, 45, and 60 min after administration of either calcitriol or vehicle (n = 5 pairs per time point). AP activity was significantly increased in the calcitriol group compared with the vehicle-treated group as early as 10 min after administration (0.132 +/- 0.003 vs. 0.151 +/- 0.005 IE/min.micron 3 X 10(3), P less than 0.02) and reached a peak 45 min after administration at which time AP activity was equal to that found in normal vitamin D-replete animals (0.193 +/- 0.003 vs. 0.192 +/- 0.002 IE/min.micron (3) X 10(3), P greater than 0.5). The speed of this response indicates it to be unlikely to depend on de novo protein synthesis.

Pathogenesis of abnormal acid-base balance in the young spontaneously hypertensive rat

1. We have previously reported reduced blood pH and plasma bicarbonate in young Okamoto-Aoki spontaneously hypertensive rats (SHR) compared with normotensive Wistar-Kyoto rats (WKY). Acid loading with 1.5% (w/v) NH4Cl as the sole drinking fluid produced identical falls in blood pH, the difference remaining significant. 2. The ability of SHR to excrete acid and alkaline loads was compared with that of WKY under metabolic cage conditions. The effects of such manipulations on urinary sodium, potassium, calcium and phosphate excretion were also determined. 3. No difference was found in the ability to excrete an acid load or to reduce urine pH. Neither total urinary ammonium ion nor titratable acid differed significantly between the strains under either baseline or acid-loading conditions. 4. Baseline urinary bicarbonate excretion was not significantly different between strains but intraperitoneal administration of NaHCO3 at 2.0 mmol/kg body weight resulted in enhanced excretion in the SHR (SHR vs WKY: 625.2 +/- 71.5 vs 381.8 +/- 40.6 mumol 24 h-1 kg-1 body weight, P less than 0.01, mean +/- SEM). 5. No difference in urinary sodium or potassium excretion was observed between SHR and WKY, but basal calcium and phosphate excretion were reduced in SHR (P less than 0.05). 6. Increased urinary bicarbonate excretion in the presence of significantly reduced plasma bicarbonate suggests reduced tubular reabsorption of bicarbonate, which may contribute to the mild metabolic acidosis in young SHR.

A water-soluble fraction from adult bone stimulates the differentiation of cartilage in explants of embryonic muscle

A water-soluble fraction of a 4 M guanidine HCl extract of demineralized adult bovine bone stimulated the differentiation of cartilage in explants of minced skeletal muscle from embryonic chick legs; cartilage was also induced by a semipurified protein preparation. Cartilage could be identified in treated cultures at 1 week with muscle from day-9 embryos, not before 2 weeks with muscle from day-12 embryos, and not before 3 weeks with muscle from day-19 embryos. The ability to respond to this water-soluble fraction by exhibiting cartilage differentiation was dose-dependent, but not confined to any particular muscle region of the day-12 embryonic leg. These observations indicate that bone-derived soluble chondroinductive agents act on cells in minced embryonic muscle preparations. The induction of cartilage is dependent upon the accessibility of the responding cells to the agents, on the concentration of inductive agents, and on the developmental age of the responsive tissue.

Chemotactic response of mesenchymal cells, fibroblasts and osteoblast-like cells to bone Gla protein

Bone gla protein (BGP) and decarboxylated bone gla protein (dBGP) were tested for chemotactic activity against stage 24 chick limb bud mesenchymal cells, chick embryonic muscle-derived fibroblasts, murine Balb/C 3T3 cells, and two lines of rat osteosarcoma cells, ROS-17/2.8 and -25/1. Both BGP and dBGP were potent chemoattractants for all the cell types except 3T3 cells. The dose response curves were bell-shaped, with maximal chemotactic response ranging from 5 pg/ml for ROS 25/1 cells to 10 ng/ml for the stage 24 limb bud cells. dBGP was equally potent a chemoattractant as BGP for all cell types tested indicating that the gamma-carboxylation of the glutamic acid residues is not required for chemotactic activity. Given this chemotactic capability, it is possible that BGP acts in bone remodelling by attracting osteogenic cells to the sites of bone resorption where BGP may be liberated or exposed.

Chemotactic response of embryonic limb bud mesenchymal cells and muscle-derived fibroblasts to transforming growth factor-beta

Transforming growth factor beta (TGF-beta) was tested for its ability to stimulate a chemotactic response in Stage 24 embryonic chick limb bud mesenchymal cells and muscle-derived fibroblasts. TGF-beta stimulated dose-dependent chemotaxis in both cell populations. Maximal chemotaxis was achieved with a concentration of 5 ng/ml for limb bud cells and as low as 15 pg/ml for muscle-derived fibroblasts. TGF-beta was not chemokinetic at these levels. Several other proteins found in bone, namely fibronectin, type I collagen, and osteonectin, were not chemotactic. However, both Bone Gla-protein and basic-FGF were found to be chemotactic but less effective than TGF-beta. Comparison with extracts of adult bone indicates that while TGF-beta is a potent chemoattractant, it does not account for all the chemotactic activity found in adult bone.

Disturbance of acid-base balance in the young spontaneously hypertensive rat

1. The acid-base status of young spontaneously hypertensive rats (SHR) was compared with that of Wistar-Kyoto rats (WKY) in the steady state, after acid loading and after blood pressure had been maintained at normal levels from weaning. Whole blood ionized calcium was measured simultaneously. 2. In the prehypertensive stage (4 weeks of age), plasma bicarbonate was significantly lower in SHR than in WKY, while blood pH did not differ significantly. 3. After 6 weeks of age, blood pH and plasma bicarbonate were significantly lower in both anaesthetized and conscious SHR than in corresponding WKY. After 7 days administration of NH4Cl in the drinking fluid, both parameters decreased significantly in both strains and the difference in pH remained constant (0.05 pH unit, P less than 0.01). 4. In none of the groups investigated did non-pH-adjusted ionized calcium differ significantly between the SHR and WKY. 5. Prevention of the development of hypertension in SHR by hydralazine treatment from weaning did not increase pH or bicarbonate compared with untreated SHR, indicating that the metabolic acidosis in the SHR was not a consequence of raised blood pressure. 6. Disturbance in acid-base balance may be involved in the pathogenesis of raised blood pressure in this animal model of genetic hypertension.

1,25(OH)2D3 receptors and endorgan response in experimental aluminium intoxication

Severe aluminium-induced osteomalacia is refractory to treatment with 1,25(OH)2D3 which frequently causes hypercalcemia. To further explore the mechanisms involved, we have utilized a model of short-term aluminium intoxication in the rat (total: 11 mg elemental aluminium in 3 weeks) to study (a) 1,25(OH)2D3 receptor status in a variety of classical and non-classical target organs for 1,25(OH)2D3; (b) circulating 1,25(OH)2D3 levels; (c) baseline duodenal calcium transport, utilising the Ussing chamber, to investigate the functional significance of receptor status in a classical target organ; and (d) duodenal calcium transport response to exogenously administered 1,25(OH)2D3. Both in the three week model and in the 16 week model (total: 41 mg elemental calcium) increased maximal specific binding capacity for 1,25(OH)2D3 (Nmax), that is, number of unoccupied receptors, was observed in nuclear fractions of all tissues studied. Receptor affinity, the apparent dissociation constant KD, was unchanged. Total binding capacity, measured after displacement of endogenous ligand by Mersalyl, that is, the sum of occupied plus non-occupied receptors, was also increased. Both circulating 1,25(OH)2D3, mucosa-to-serosa calcium flux (Jms) and net calcium flux (Jnet) were reduced under baseline conditions, suggesting the lack of a direct relationship between receptor expression and endorgan response. Following exogenous 1,25(OH)2D3 administration, calcium Jms and Jnet were significantly lower in the aluminium intoxicated animals, with the increment induced in Jnet in aluminium intoxicated animals being 63% of that induced in controls. Our data suggest that resistance to the action of 1,25(OH)2D3 in aluminium intoxication is postreceptor in nature.

Feedback control of selected biosynthetic activities of chondrocytes in culture

The syntheses of proteoglycans and proteins by chondrocytes from the Swarm rat chondrosarcoma in primary cultures were modulated on the addition of matrical molecules. In the presence of hyaluronan, collagen or proteoglycan aggregates the synthesis of proteoglycans was depressed. The synthesis of collagen was also depressed in the presence of hyaluronan or collagen. In the presence of proteoglycan monomers, the incorporation of 35S-sulfate was enhanced in proportion to the concentration of the additive in the medium; the synthesis of protein was unaffected. The proteoglycan monomers synthesized in the presence of proteoglycan monomers were larger than those synthesized in their absence. In combinations, the exogenous macromolecules did not affect the selected biosynthetic activities to an extent greater than that which they exerted separately. The data suggest, however, that the proteoglycan monomers can counteract the inhibitory effects of the macromolecules which are inhibitory. The data, moreover, suggest that the chondrocytes of the Swarm rat chondrosarcoma have the potential to discriminate between proteoglycan monomers produced by self and those produced by chondrocytes of hyaline cartilages.

Abnormal vitamin D metabolism, intestinal calcium transport, and bone calcium status in the spontaneously hypertensive rat compared with its genetic control

Abnormalities of intestinal calcium absorption and the vitamin D axis in the spontaneously hypertensive rat (SHR) are controversial. The present report documents a reduction in circulating 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in the 12-14-wk-old male SHR with evidence of its functional significance. Both plasma 1,25(OH)2D3 and mucosa-to-serosa duodenal calcium flux (Jm-s), measured by the Ussing chamber, were significantly lower (approximately 60% of value in Wistar-Kyoto rats [WKY]) in SHR on both normal (1%) and low (0.1%) calcium diets than in corresponding control WKY. Low dietary calcium increased both 1,25(OH)2D3 and Jm-s by approximately 80% in SHR and WKY, with levels of both parameters rising in the SHR to levels found in the WKY under baseline conditions. The latter fact suggests the improbability of intestinal resistance to the action of 1,25(OH)2D3 in the SHR. Plasma 25-hydroxyvitamin D3 (25(OH)D3) was not significantly different between the strains. Intraperitoneal 1,25(OH)2D3 increased Jm-s in 12-14-wk-old SHR to levels observed in equivalent WKY. In 20-24-wk-old SHR, calcium deprivation was associated with significantly reduced Jm-s compared with equivalent WKY. Bone density and bone calcium content in 20-30-wk-old SHR were significantly reduced. In summary, we provide evidence that the SHR was unable to sustain appropriate circulating levels of 1,25(OH)2D3, an impairment which resulted in reduced duodenal calcium absorption.

The risks and benefits of a low protein-essential amino acid-keto acid diet

Twelve patients with progressive renal failure were placed on a very low protein diet supplemented by an essential amino acid-keto acid mixture for six to twelve months. Total daily intake was 0.04 g nitrogen/kg and 50 kcal/kg. Eight subjects had a significant change in the slope of reciprocal plasma creatinine, becoming less steep and in two cases positive. GFR did not improve, but in four patients the decline over twelve months was less than 0.5 mliter/min. There were significant falls in blood and urinary urea, serum phosphate PTH and calcium X phosphate product. Body wt decreased during the first three months. Arm muscle circumference fell by 0.9 cm (P less than 0.005). Serum albumin and transferrin levels did not change significantly. Muscle mass and plasma creatinine fell simultaneously in several patients. Creatinine excretion per kg muscle mass, assessed anthropometrically, declined by 21% in the first three months. This diet may slow the decline in renal function in a proportion of patients. However, muscle mass can be lost. Serum protein levels do not accurately reflect nutritional changes. A fall in plasma creatinine may not be due to improved GFR but instead to altered creatinine metabolism.

1,25-dihydroxycholecalciferol and parathyroid hormone in advanced chronic renal failure: effects of simultaneous protein and phosphorus restriction

Vitamin D3 metabolites and immunoreactive parathyroid hormone (iPTH) were measured in sera obtained from subjects with advanced chronic renal failure (CRF) (creatinine clearance less than 10 ml/min) before and after 3 months on a diet very low in protein (less than 0.2 g/kg/day), phosphorus (less than 500 mg/day), and supplemented with a mixture of essential amino acids and ketoacid analogues of essential amino acids. iPTH and phosphate fell in all subjects (p less than 0.02). 1,25-dihydroxycholecalciferol (1,25[OH]2D3) fell in all but one of the subjects (p less than 0.02), while no significant change was seen in creatinine clearance or in serum 25-hydroxycholecalciferol (25[OH]D3) levels. A strongly positive correlation was found between initial serum levels of 25(OH)D3 and 1,25(OH)2D3 (r = 0.95, p less than 0.001). Thus in contrast with the reported effects of dietary phosphorus reduction in subjects with early and moderate CRF and in normal subjects, this regime was associated with decreased 1,25(OH)2D3 levels in subjects with advanced CRF.

Partial isolation and characterization of a chemotactic factor from adult bovine bone for mesenchymal cells

Demineralized adult bone matrix has the capacity to initiate de novo ectopic endochondral bone formation 2-3 weeks following intramuscular implantation into suitable hosts. An early step in this process is the migration of mesenchymal cells to the implant site; these cells later differentiate into cartilage and bone. Adult bone has been shown to contain a number of bioactive factors, such as chemotactic factors for various cell types, including osteoblasts. We have used embryonic chick limb bud mesenchymal cells to construct an in vitro assay for testing chemotactic activity derived from bone matrix extracts. With a modified Boyden chamber, water-soluble components from a 4 M guanidinium chloride extract of demineralized adult bovine bone matrix were found to stimulate the directional migration of these chick embryonic limb bud mesenchymal cells as well as embryonic muscle-derived fibroblasts and cells derived from embryonic skin. The chemotactic activity was destroyed by treatment with heat (100 degrees C) or trypsin. Partial purification by molecular sieve chromatography suggested that the chemotactic factor(s) has a molecular weight of between 50,000 and 90,000. This factor can be separated from bone matrix-derived chondrogenic stimulating activity by either ion exchange or molecular sieve chromatography. These observations confirm that bone matrix contains a chemoattractant for mesenchymal cells that may be important for in vivo recruitment of cells as part of the process of ectopic bone formation or in cases of bone repair.

The in vitro chondrogenic response of limb-bud mesenchyme to a water-soluble fraction prepared from demineralized bone matrix

Demineralized adult bone matrix initiates de novo ectopic endochondral ossification 2-3 weeks following its intramuscular implantation into adult animals. This phenomenon appears to be similar, in some ways, to inductive cell-matrix interactions which regulate cartilage and bone formation during development. In the present study, we used embryonic chick limb-bud mesenchymal-cell cultures to bioassay extracts of demineralized bone matrix for chondrogenic activity. Guanidinium-chloride (4 M) extracts of demineralized bovine bone were dialyzed against buffers of decreasing ionic strength and then cold water. The cold-water-soluble fraction was found to stimulate chondrogenesis in intermediate-density limb-bud cell cultures (2.2 X 10(6) cells per 35-mm dish), as revealed by visual inspection with phase optics, toluidine-blue staining of fixed plates, and [35S] sulfate incorporation in the cell layer. Further fractionation of this material by anion-exchange, carbohydrate-affinity, and molecular-sieve chromotography produced a semipurified preparation possessing chondrogenic-stimulating activity at doses ranging from 3 to 10 micrograms/ml. The in vitro chondrogenic response of limb-bud mesenchymal cells was dose-dependent, required a minimal initial plating density of 2.08 X 10(5) cells/mm2 of culture dish, and developed gradually over 8-10 days. At an optimal dose of extract, a continuous exposure period of at least 2-3 days was necessary to produce detectable chondrogenic stimulation. In addition, the amount of cartilage formed following an 8-day exposure was markedly influenced by the culture 'age' of the mesenchymal cells (i.e., the time between plating and the start of treatment).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood pressure development of the spontaneously hypertensive rat after concurrent manipulations of dietary Ca2+ and Na+. Relation to intestinal Ca2+ fluxes

The blood pressure of the spontaneously hypertensive rat (SHR) is influenced by the Ca2+ content of its diet. As the SHR's greater dependence on dietary calcium may reflect a defect in intestinal calcium absorption, we measured in vitro unidirectional Ca2+ flux (J) in the duodenum-jejunum (four segments each) of the SHR (n = 6) and the normotensive Wistar-Kyoto rat (WKY; n = 6) by a modified Ussing apparatus. Because of the known and postulated interactions between Ca2+ and Na+ in both intestinal and vascular tissue, we assessed in vivo the influence of a concurrent manipulation of Na+ intake (three levels: 0.25%, 0.45%, and 1.0%) on the blood pressure development of SHRs (n = 35) and WKYs (n = 35), between 6 and 20 wk of age, exposed to three levels of dietary calcium (0.1, 1.0, and 2%). Net calcium flux (Jnet) (mean +/- SEM) was significantly (P less than 0.01) lower in the SHR (-2.8 +/- 6.3 nmol/cm2 X h) than in the WKY (34.6 +/- 8.8 nmol/cm2 X h). The SHR's decreased Jnet resulted from a significantly (P less than 0.03) lower mucosa-to-serosa flux (Jm-s) in the SHR (41.0 +/- 5.6 nmol/cm2 X h) compared with the Jm-s of the WKY (70.1 +/- 9.1 nmol/cm2 X h). Serosa-to-mucosa flux for calcium did not differ between the SHR (43.8 +/- 6.6 nmol/cm2 X h) and the WKY (35.5 +/- 8.0 nmol/cm2 X h). The SHR's decreased (P less than 0.002) Jm-s was confirmed by additional measurements in SHRs and WKYs. Jm-s was 36.2 +/- 3.7 nmol/cm2 X h in the SHRs (n = 11) and 64.4 +/- 6.7 nmol/cm2 X h in the WKYs (n = 9). The provision of an increased dietary Ca2+ (2% by weight) and increased Na+ (1%) to the SHR prevented the emergence of hypertension (P less than 0.001) (mean +/- SEM systolic blood pressure at 20 wk of age; 135 +/- 5 mmHg for the 2% Ca2+, 1% Na+ SHR vs. 164 +/- 2 mmHg for the control diet SHR). Ca2+ (0.1%) and Na+ (0.25%) restriction accelerated the SHR's hypertension (192 +/- 2 mmHg) (P less than 0.001) and was associated with higher pressures in the WKY (146 +/- 4 mmHg in the restricted WKY vs. 134 +/- 4 mmHg in the control WKY). In a parallel group of 24 SHRs and 24 WKYs fed one of three diets (2% Ca2+/1% Na+; 1% Ca2+/0.45% Na+; or 0.1% Ca2+/0.25% Na+), the heart (P < 0.05) and kidney (P = 0.08) weight of the SHRs varied depending on the diet at 20 wk of age. Low Ca2+ and Na+ intake was associated with increased heart weight (1.6+/-0.9 g) compared with the normal diet for SHR (1.51+/-0.07 g). Increased Ca2+ and Na+ intake was associated with a significantly (P = 0.05) lower heart weight in the SHR (1.37+/-0.03 g) and in the WKY (1.35+/-0.06 g) compared with their normal diet controls. These findings show one mechanism for the SHR's depressor response to supplemental dietary Ca2+ and, in part, explain the sodium dependence of calcium's cardiovascular protective effect.

The effect of vitamin A deficiency and fluoride on glycosaminoglycan metabolism in bone

The effects of fluoride intake and vitamin A deficiency on glycosaminoglycan metabolism in vivo were investigated. Weanling female rats were fed either a vitamin A deficient diet ad libitum, a vitamin A supplemented diet pair-fed to the deficient animals, or the vitamin A supplemented diet ad libitum. Additionally, each vitamin A dietary group was divided into three subgroups with the animals receiving water containing 0, 10 or 50 ppm fluoride. The results showed that the groups receiving 10 and 50 ppm fluoride at all dietary levels of vitamin A had significantly higher in vivo 35SO4 incorporation in both the epiphyseal and diaphyseal regions of the bone than the animals receiving 0 ppm fluoride. The vitamin A deficient animals incorporated significantly less 35SO4 into glycosaminoglycans in the epiphyseal and diaphyseal regions of the bone compared to the pair-fed, vitamin A sufficient animals for all three fluoride receiving groups. There was no interaction between fluoride intake and dietary vitamin A levels on 35SO4 incorporation into glycosaminoglycans. Fluoride either increased sulfation or turnover of glycosaminoglycans.

Changes in blood pressure and renal function after parathyroidectomy in primary hyperparathyroidism

Changes in blood pressure and renal function were investigated in 62 patients with primary hyperparathyroidism treated surgically, in an attempt to assess whether or not hypertension and renal impairment should be regarded as important indications for parathyroidectomy. 29% were hypertensive pre-operatively and the blood pressure remained elevated after parathyroidectomy in all of these patients. Hypertension developed for the first time after parathyroidectomy in 45% of those patients who were normotensive before surgery. Renal function was normal initially in 73% and mild renal impairment developed after surgery in 9% of these patients. At the end of the follow-up period, the prevalence of hypertension was higher in patients with renal impairment pre-operatively (88%) than in those with normal renal function (51%). We conclude that hypertension alone should not be regarded as an indication for parathyroidectomy in asymptomatic hyperparathyroidism. No firm conclusions can be reached about the importance of mild renal failure as an indication for surgery and the question is unlikely to be resolved without conducting a prospective controlled trial.