Carotenoids and human health

Oxidative stress is an important contributor to the risk of chronic diseases. Dietary guidelines recommend increased consumption of fruits and vegetables to combat the incidence of human diseases such as cancer, cardiovascular disease, osteoporosis and diabetes. Fruits and vegetables are good sources of antioxidant phytochemicals that mitigate the damaging effect of oxidative stress. Carotenoids are a group of phytochemicals that are responsible for different colors of the foods. They are recognized as playing an important role in the prevention of human diseases and maintaining good health. In addition to being potent antioxidants some carotenoids also contribute to dietary vitamin A. There is scientific evidence in support of the beneficial role of phytochemicals in the prevention of several chronic diseases. Although the chemistry of carotenoids has been studied extensively, their bioavailability, metabolism and biological functions are only now beginning to be investigated. Recent interest in carotenoids has focused on the role of lycopene in human health. Unlike some other carotenoids, lycopene does not have pro-vitamin A properties. Because of the unsaturated nature of lycopene it is considered to be a potent antioxidant and a singlet oxygen quencher. This article will review carotenoids in general and lycopene in particular for their role in human health.

The adenovirus E1A proteins induce apoptosis, which is inhibited by the E1B 19-kDa and Bcl-2 proteins

Cooperation between the adenovirus E1A and E1B oncogenes is required for transformation of primary quiescent rodent cells. Although expression of E1A alone will stimulate cell proliferation sufficient to initiate transformed focus formation, proliferation fails to be sustained and foci degenerate. Coexpression of either the 19-kDa or 55-kDa E1B oncoproteins with E1A permits high-frequency transformation by overcoming this cytotoxic response. Without E1B 19-kDa protein expression, however, transformants remain susceptible to induction of cell death. Rapid loss of viability is coincident with nucleolytic cleavage of DNA in intranucleosomal regions and chromatin condensation, hallmarks of programmed cell death (apoptosis). Furthermore, overexpression of a known suppressor of apoptosis, the Bcl-2 protooncogene, can rescue E1A-induced focus degeneration. Thus E1A-dependent stimulation of cell proliferation is accompanied by apoptosis and thereby insufficient to singly induce transformation. High-frequency transformation requires a second function encoded by the E1B 19-kDa protein to block apoptosis.

Lamin proteolysis facilitates nuclear events during apoptosis

Expression of the adenovirus E1A oncogene stimulates both cell proliferation and p53-dependent apoptosis in rodent cells. p53 implements apoptosis in all or in part through transcriptional activation of bax, the product of which promotes cell death. The adenovirus E1B 19K product is homologous in sequence and in function to Bcl-2, both of which bind to and inhibit the activity of Bax and thereby suppress apoptosis. The E1B 19K protein also interacts with the nuclear lamins, but the role of this interaction in the regulation of apoptosis is not known. Lamins are, however, substrates for members of the interleukin-1 beta-converting enzyme (ICE) family of cysteine proteases that are activated during apoptosis and function downstream of Bcl-2 in the cell death pathway. lamins are degraded during E1A-induced p53-dependent apoptosis. Lamin A and C are cleaved into 47- and 37-kD fragments, respectively, and the site of proteolysis is mapped to a conserved aspartic acid residue at position 230. The cleavage of lamins during apoptosis is consistent with the activation of an ICE-related cysteine protease down-stream of p53. No lamin protease activity was detected in cells expressing the E1B 19K protein, indicating that 19K functions upstream of protease activation in inhibiting apoptosis. Substitution of the aspartic acid at the cleavage site produced a mutant lamin protein that was resistant to proteolysis both in vitro and in vivo. Expression of uncleavable mutant lamin A or B attenuated apoptosis, delaying cell death and the associated DNA fragmentation by 12 h. Mutant lamin expressing cells failed to show the signs of chromatin condensation and nuclear shrinkage typical of cell death by apoptosis. Instead, the nuclear envelope collapsed and the nuclear lamina remained intact. However, the late stage of apoptosis was morphologically unaltered and formation of apoptotic bodies was evident. Thus, lamin breakdown by proteolytic degradation facilitates the nuclear events of apoptosis perhaps by facilitating nuclear breakdown.

The E1B 19K protein blocks apoptosis by interacting with and inhibiting the p53-inducible and death-promoting Bax protein

The E1B 19K protein is a potent apoptosis inhibitor and the putative adenovirus Bcl-2 homolog. To investigate the mechanism of apoptosis regulation, 19K-interacting cellular proteins were identified using the yeast two-hybrid system, and Bax was one of seven 19-K interacting clones. Residues 50-78 of Bax containing a conserved region designated Bcl-2 homology region 3 (BH3) were sufficient for specific binding to both the E1B 19K and Bcl-2 proteins. The Bax-E1B 19K interaction was detectable in vitro and in lysates from mammalian cells, and Bax expression antagonized E1B 19K protein function. bax mRNA and protein levels were p53-inducible with kinetics identical to that of p21/Waf-1/Cip-1, and E1B 19K and Bcl-2 expression did not affect Bax or p21/Waf-1/Cip-1 accumulation. In cells where p53 was mutant, Bax expression induced apoptosis, suggesting that Bax was sufficient for apoptosis, and acted downstream of p53. p53 may simultaneously activate the transcription of genes required for both growth arrest (p21/Waf-1/Cip-1) and death (bax), and E1B 19K and Bcl-2 may act distally and function through interaction with and antagonism of Bax to prevent apoptosis. With the death pathway disabled, induction of growth arrest by p53 can then be manifested.

Functional complementation of the adenovirus E1B 19-kilodalton protein with Bcl-2 in the inhibition of apoptosis in infected cells

Expression of the adenovirus E1A oncogene induces apoptosis which impedes both the transformation of primary rodent cells and productive adenovirus infection of human cells. Coexpression of E1A with the E1B 19,000-molecular-weight protein (19K protein) or the Bcl-2 protein, both of which have antiapoptotic activity, is necessary for efficient transformation. Induction of apoptosis by E1A in rodent cells is mediated by the p53 tumor suppressor gene, and both the E1B 19K protein and the Bcl-2 protein can overcome this p53-dependent apoptosis. The functional similarity between Bcl-2 and the E1B 19K protein suggested that they may act by similar mechanisms and that Bcl-2 may complement the requirement for E1B 19K expression during productive infection. Infection of human HeLa cells with E1B 19K loss-of-function mutant adenovirus produces apoptosis characterized by enhanced cytopathic effects (cyt phenotype) and degradation of host cell chromosomal DNA and viral DNA (deg phenotype). Failure to inhibit apoptosis results in premature host cell death, which impairs virus yield. HeLa cells express extremely low levels of p53 because of expression of human papillomavirus E6 protein. Levels of p53 were substantially increased by E1A expression during adenovirus infection. Therefore, E1A may induce apoptosis by overriding the E6-induced degradation of p53 and promoting p53 accumulation. Stable Bcl-2 overexpression in HeLa cells infected with the E1B 19K- mutant adenovirus blocked the induction of the cyt and deg phenotypes. Expression of Bcl-2 in HeLa cells also conferred resistance to apoptosis mediated by tumor necrosis factor alpha and Fas antigen, which is also an established function of the E1B 19K protein. A comparison of the amino acid sequences of Bcl-2 family members and that of the E1B 19K protein indicated that there was limited amino acid sequence homology between the central conserved domains of E1B 19K and Bcl-2. This domain of the E1B 19K protein is important in transformation and regulation of apoptosis, as determined by mutational analysis. The limited sequence homology and functional equivalency provided further evidence that the Bcl-2 and E1B 19K proteins may possess related mechanisms of action and that the E1B 19K protein may be the adenovirus equivalent of the cellular Bcl-2 protein.

Factor independent activation of rrnB P1. An "extended" promoter with an upstream element that dramatically increases promoter strength

The extraordinary strength of the Escherichia coli rRNA promoter rrnB P1 derives primarily from sequences upstream of the core (-10, -35) region. We find that sequences between -40 and -60 increase the activity of this promoter at least 30-fold in vitro and in vivo. This region, which we refer to as the upstream (UP) element, is located between the -35 consensus hexamer and the previously characterized binding sites for the rRNA transcription factor Fis. The effect of the UP element is independent of Fis in vivo, and independent of any other proteins besides RNA polymerase (RNAP) in vitro. The UP element increases the overall second-order rate constant for association of RNAP with the promoter (ka) and probably the apparent overall first-order isomerization constant (ki). Together with the previously reported protection of the UP element region by RNAP in footprinting experiments, these results indicate that rrnB P1 has an "extended" promoter structure, consisting of the UP element and the core promoter region. We find that the UP element is a separable promoter module that can function to increase the activity of the lac core promoter in an rrnB P1-lac hybrid promoter construct. A functional UP element is not absolutely essential for stimulation of rrnB P1 by the Fis protein.

Lycopene

Oxidative stress is now recognized as an important etiological factor in the causation of several chronic diseases including cancer, cardiovascular diseases, osteoporosis, and diabetes. Antioxidants play an important role in mitigating the damaging effects of oxidative stress on cells. Lycopene, a carotenoid antioxidant, has received considerable scientific interest in recent years. Epidemiological, tissue culture, and animal studies provide convincing evidence supporting the role of lycopene in the prevention of chronic diseases. Human intervention studies are now being conducted to validate epidemiological observations and to understand the mechanisms of action of lycopene in disease prevention. To obtain a better understanding of the role of lycopene in human health, this chapter reviews the most recent information pertaining to its chemistry, bioavailability, metabolism, role in the prevention of prostate cancer and cancer of other target organs, its role in cardiovascular diseases, osteoporosis, hypertension, and male infertility. A discussion of the most relevant molecular markers of cancer is also included as a guide to future researchers in this area. The chapter concludes by reviewing global intake levels of lycopene, suggested levels of intake, and future research directions.

Modulation of p53-mediated transcriptional repression and apoptosis by the adenovirus E1B 19K protein

BRK cell lines that stably express adenovirus E1A and a murine temperature-sensitive p53 undergo apoptosis when p53 assumes the wild-type conformation. Expression of the E1B 19,000-molecular-weight (19K) protein rescues cells from this p53-mediated apoptosis and diverts cells to a growth-arrested state. As p53 likely functions as a tumor suppressor by regulating transcription, the ability of the E1B 19K protein to regulate p53-mediated transactivation and transcriptional repression was investigated. In promoter-reporter assays the E1B 19K did not block p53-mediated transactivation but did alleviate p53-mediated transcriptional repression. E1B 19K expression permitted efficient transcriptional activation of the p21/WAF-1/cip-1 mRNA by p53, consistent with maintenance of the growth arrest function of p53. The E1B 19K protein is thereby unique among DNA virus-transforming proteins that target p53 for inactivation in that it selectively modulates the transcriptional properties of p53. The E1B 19K protein also rescued cells from apoptosis induced by inhibitors of transcription and protein synthesis. This suggests that cell death may result from the inhibition of expression of survival factors which function to maintain cell viability. p53 may induce apoptosis through generalized transcriptional repression. In turn, the E1B 19K protein may prevent p53-mediated apoptosis by alleviating p53-mediated transcriptional repression.

Parathyroid hormone- and prostaglandin E1-response in a selected population of bone cells after repeated subculture and storage at -80C

Five different cell populations, designated I to V, were isolated from minced newborn rat calveria by 5-sequential 20 min incubations with an enzyme mixture containing collagenase, elastase and DNAse. In primary culture, all five populations responded to parathyroid hormone (PTH) to a different degree, population IV giving the highest increase in cyclic-3'5'-adenosine monophosphate (cAMP) level. None of the five populations gave any response to calcitonin. Upon subsequent subcultures, all populations, except population IV, either lost or considerably decreased their response to PTH. Population IV gave a two to three-fold increase in cAMP concentration in response to PTH up to the third subculture. No morphological differences could be observed among the five populations. The third subculture of population IV cells that had been stored in 10% glycerol at -80C for four months was subsequently thawed and subcultured to the sixth subculture. These cells still responded to PTH with an increase in cAMP level. In a second experiment, 5 different cell populations designated I to V were isolated in a similar way by incubation with collagenase and DNAse. The maximum response to PTH was found in population 3. The preservation of the PTH-responsiveness of this population, after subculturing, freezing, storing in 10% glycerol at -80 C and subsequent subculturing, was likewise demonstrated. The hormone-responsiveness of cells from the sixth subculture of previously frozen and thawed population IV cells was further analyzed. These cells responded to PTH at a concentration of 0.1 U/ml to 5U/ml and to prostaglandin E1 (PGE1) at a concentration of 0.1 microng/ml to 10 microng/ml. The time course of action on population IV of PTH was found to be different from that of PGE1, suggesting a possible difference in the regulation of intracellular cAMP levels by these hormones.

Bcl-2 and the ICE family of apoptotic regulators: making a connection

Apoptosis, a genetically programmed mechanism of eliminating cells in response to a variety of stimuli, provides protection against cancer and viral infections as well as maintenance of homeostasis in living organisms. Two classes of molecules, the Bcl-2 family of regulators and the ICE family of proteases, have emerged from different vertebrate, invertebrate and viral systems that have been used to elucidate the pathways leading to apoptosis. However, no connection between these two disparate families of apoptotic regulators has been convincingly established. In reviewing the recent advances pertaining to the Bcl-2 and ICE-related protein families, one can address the question of a functional relationship between the two classes of proteins.

An overview and recent progress in the chemistry of uranium extraction from seawater

This review provides a brief background on the extraction of uranium from seawater as well as recent work by the United States Department of Energy on this project. The world's oceans contain uranium at 3 parts per billion, and despite this low concentration, there has been historical interest in harvesting it, mainly in Japan in the 1980s and the United States in this decade. Improvements in materials, chemistry, and deployment methods have all been made, with the ultimate goal of lower cost. This has been partially realized, dropping from approximately $2000 per kg U₃O₈ extracted in 1984 to $500 per kg today, although this is not yet competitive with terrestrial uranium. This technology may become cost-competitive if the cost of land-based uranium rises, especially if seawater extraction technology is improved further. The coordination chemistry aspects of the project are described in more detail, exploring the functional groups that are present on typical polymer sorbents as well as small-molecule analogues of these ligands. Selectivity for uranium over other metals, particularly vanadium, remains problematic, and techniques to both quantify binding strength and selectivity in order to overcome this issue are essential for future cost improvements.

Carcinoma of the rectal pouch following restorative proctocolectomy. Report of a case

A case of adenocarcinoma developing in the pouch following restorative proctocolectomy is presented. This seems to be the third reported in the literature. The carcinoma developed from the remnants of precancerous rectal mucosa left in the muscular rectal cuff. The patient had been suffering from ulcerative colitis for 17 years prior to the development of the malignancy. He presented with features of subacute intestinal obstruction. Diagnosis was by sigmoidoscopic examination of the pouch and biopsy. He was treated with abdominoperineal resection of the pouch and rectum, followed by chemotherapy.

Long-term effects of physiologic concentrations of dexamethasone on human bone-derived cells

Bone cells derived from human trabecular explants display osteoblastic features. We examined the modulation of alkaline phosphatase activity and cAMP production as the result of exposing trabecular explants to physiologic concentrations of dexamethasone for 4 weeks during cellular outgrowth and subculture. Cells treated with dexamethasone were observed to grow generally more slowly than control cells. Cells appeared larger and more polygonal, and staining for alkaline phosphatase was more intense in the dexamethasone-exposed cultures. There was a progressive increase in cellular PTH responsiveness with increasing duration of exposure of cells to dexamethasone. Cells grown for 6 weeks in 3 x 10(-8) M dexamethasone had a 10-fold increase in PTH-stimulated cyclic AMP accumulation. Dexamethasone-treated cells also had a significantly increased alkaline phosphatase activity. 1,25-(OH)2D3-stimulated alkaline phosphatase activity was increased approximately 20-fold. cAMP responses were significantly increased to PTH (21.7-fold), PGE1 (2.67-fold), and forskolin (4.81-fold), but not to cholera toxin. Dexamethasone-treated cells also had a mean decrease in 1,25-(OH)2D3-stimulated osteocalcin production to 26.2% of control values (p less than 0.001). Hydrocortisone treatment gave rise to similar effects but of smaller magnitude than those of dexamethasone. Testosterone did not have a significant effect on alkaline phosphatase activity or cAMP production. Skin fibroblasts showed a significant enhancement of alkaline phosphatase activity in response to dexamethasone, but of a much smaller magnitude than in bone cells. The phenotypic changes induced by long-term culture in dexamethasone are consistent with the promotion of a more differentiated osteoblastic phenotype.

Lycopene consumption decreases oxidative stress and bone resorption markers in postmenopausal women

INTRODUCTION

Oxidative stress induced by reactive oxygen species (ROS) is associated with the risk of osteoporosis, and can be reduced by certain dietary antioxidants. Lycopene is an antioxidant known to decrease the risk of age-related chronic diseases, such as cancer. However, the role of lycopene in osteoporosis has not yet been investigated.

MATERIALS AND METHODS

In a cross-sectional study, 33 postmenopausal women aged 50-60 years provided seven-day dietary records and blood samples. Serum samples were used to measure serum lycopene, lipid peroxidation, protein thiols, bone alkaline phosphatase (BAP), and cross-linked N-telopeptides of type I collagen (NTx). The serum lycopene per kilogram body weight of the participants was grouped into quartiles and associated with the above serum parameters using one-way ANOVA and the Newman-Keuls post-test.

RESULTS

The results showed that groups with higher lycopene intake, as determined from the dietary records, had higher serum lycopene (p<0.02). A higher serum lycopene was found to be associated with a low NTx (p<0.005). Similarly, groups with higher serum lycopene had lower protein oxidation (p<0.05).

DISCUSSION

In conclusion, these results suggest that the dietary antioxidant lycopene reduces oxidative stress and the levels of bone turnover markers in postmenopausal women, and may be beneficial in reducing the risk of osteoporosis.

Gene expression profiling of low selenium status in the mouse intestine: transcriptional activation of genes linked to DNA damage, cell cycle control and oxidative stress

The essential trace mineral selenium (Se) has been shown previously to inhibit intestinal, prostate, lung and liver tumor development and associated mortality in both experimental animals and humans. Although Se is likely to be one of the most powerful cancer chemopreventive agents in the human diet, its mechanism of action is unknown. To better understand the biological consequences of alterations in Se status, the gene expression profile associated with low Se status in the intestine of C57Bl/6J mice was analyzed. Mice were fed either a high fat (14%), torula yeast-based, Se-deficient diet (<0.01 mg/kg) or the same diet supplemented with a high level of dietary Se (1 mg/kg, as seleno-L-methionine) for 90 d. Use of high density oligonucleotide arrays representing 6347 genes revealed that low Se status results in a differential gene expression pattern indicative of activation of genes involved in DNA damage, oxidative stress and cell cycle control, and a decrease in the expression of genes involved in detoxification. These results suggest that suboptimal intake of a single trace mineral can have broad effects on gene expression patterns, providing a framework for understanding the multiple beneficial effects of Se in cancer chemoprevention and human health.

Pseudohypoparathyroidism with osteitis fibrosa cystica: direct demonstration of skeletal responsiveness to parathyroid hormone in cells cultured from bone

A young girl had tibial osteotomies at age 14 for genu valgum and then had recurrent tibial cysts over a number of years. Hypocalcemia and hyperphosphatemia were first noted at age 21. The diagnosis of pseudohypoparathyroidism was made at age 28, when elevated plasma PTH was detected. Clinical and biochemical features, including a PTH response test and assay of RBC Gs, established the diagnosis of pseudohypoparathyroidism type 1b. Failure to suppress plasma PTH with vitamin D therapy led to an exacerbation of her cystic bone disease; there were widespread lytic lesions radiologically, most of which took up [99mTc]diphosphonate on bone scan. Microradioscopy revealed evidence of resorption of phalangeal tufts. Bone biopsy showed osteitis fibrosa cystica. During an orthopedic procedure, trabecular bone fragments were taken from her right humerus, and bone-derived cells cultured using an explant technique. The cultured cells were osteoblast-like in morphology, fully responsive to PTH, cholera toxin, forskolin, and PGE1 in vitro, and had an alkaline phosphatase and osteocalcin response to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. Following this examination of skeletal responsiveness, attempts were made to suppress the elevated plasma PTH levels and symptomatic bone disease by optimizing therapy with oral 1,25-(OH)2D3. When bone pain associated with the cystic bone disease failed to resolve, the patient underwent total parathyroidectomy, following which the bone pain gradually resolved. This is the first direct demonstration of PTH responsiveness in cultured bone cells in the syndrome of pseudohypoparathyroidism with osteitis fibrosa cystica.

Supplementation with the antioxidant lycopene significantly decreases oxidative stress parameters and the bone resorption marker N-telopeptide of type I collagen in postmenopausal women

To date, no intervention studies have been published demonstrating the effect of the antioxidant lycopene on bone. Postmenopausal women supplemented with lycopene had significantly increased antioxidant capacity and decreased oxidative stress and the bone resorption marker N-telopeptide (NTx). Lycopene decreases bone resorption markers and may reduce the risk of osteoporosis.

INTRODUCTION

We have previously shown in vitro and in vivo that lycopene from tomato is associated with a protective effect on bone, but lycopene intervention studies have not been reported. Our aim was to carry out a randomized controlled intervention study to determine whether lycopene would act as an antioxidant to decrease oxidative stress parameters, resulting in decreased bone turnover markers, thus reducing the risk of osteoporosis in postmenopausal women.

METHODS

Sixty postmenopausal women, 50-60 years old, were recruited. Following a 1-month washout without lycopene consumption, participants consumed either (N = 15/group): (1) regular tomato juice, (2) lycopene-rich tomato juice, (3) tomato Lyc-O-Mato lycopene capsules, or (4) placebo capsules, twice daily for total lycopene intakes of 30, 70, 30, and 0 mg/day respectively for 4 months. Serum collected after the washout, 2 and 4 months of supplementation, was assayed for cross-linked aminoterminal N-telopeptide, carotenoid content, total antioxidant capacity (TAC), lipid, and protein oxidation.

RESULTS

Participants who consumed juice or lycopene capsules were analyzed in one group designated "LYCOPENE-supplemented". Repeated measures ANOVA showed that LYCOPENE-supplementation for 4 months significantly increased serum lycopene compared to placebo (p < 0.001). LYCOPENE-supplementation for 4 months resulted in significantly increased TAC (p < 0.05) and decreased lipid peroxidation (p < 0.001), protein oxidation (p < 0.001), and NTx (p < 0.001). These decreases in lipid peroxidation, protein oxidation, and NTx were significantly different from the corresponding changes resulting from placebo supplementation (p < 0.05, p < 0.005, and p < 0.02, respectively).

CONCLUSIONS

Our findings suggest that the antioxidant lycopene is beneficial in reducing oxidative stress parameters and the bone resorption marker NTx.

Bcl-2 blocks p53-dependent apoptosis

Adenovirus E1A expression recruits primary rodent cells into proliferation but fails to transform them because of the induction of programmed cell death (apoptosis). The adenovirus E1B 19,000-molecular-weight protein (19K protein), the E1B 55K protein, and the human Bcl-2 protein each cause high-frequency transformation when coexpressed with E1A by inhibiting apoptosis. Thus, transformation of primary rodent cells by E1A requires deregulation of cell growth to be coupled to suppression of apoptosis. The product of the p53 tumor suppressor gene induces apoptosis in transformed cells and is required for induction of apoptosis by E1A. The ability of Bcl-2 to suppress apoptosis induced by E1A suggested that Bcl-2 may function by inhibition of p53. Rodent cells transformed with E1A plus the p53(Val-135) temperature-sensitive mutant are transformed at the restrictive temperature and undergo rapid and complete apoptosis at the permissive temperature when p53 adopts the wild-type conformation. Human Bcl-2 expression completely prevented p53-mediated apoptosis at the permissive temperature and caused cells to remain in a predominantly growth-arrested state. Growth arrest was leaky, occurred at multiple points in the cell cycle, and was reversible. Bcl-2 did not affect the ability of p53 to localize to the nucleus, nor were the levels of the p53 protein altered. Thus, Bcl-2 diverts the activity of p53 from induction of apoptosis to induction of growth arrest, and it is thereby identified as a modifier of p53 function. The ability of Bcl-2 to bypass induction of apoptosis by p53 may contribute to its oncogenic and antiapoptotic activity.

Binding of intact parathyroid hormone to rat osteosarcoma cells: major contribution of binding sites for the carboxyl-terminal region of the hormone

Most studies of PTH receptor binding have been carried out with amino-terminal radioligands which only detect binding within that region of the hormone molecule. We studied the binding of electrolytically labeled intact bovine PTH [bPTH-(1-84)], and its amino-terminal fragment, bPTH-(1-34) to intact cloned rat osteosarcoma cells (ROS 17/2.8). We also measured the effects of these hormones on cell cAMP accumulation. Binding equilibrium for the two radioligands was reached by 2 h of incubation at 22 C. However, the cells had higher binding capacity (8-9% or 0.22-0.25 fmol/2 X 10(6) cells) for [125I]bPTH-(1-84) than for [125I]bPTH-(1-34) (4% or 0.11 fmol/2 X 10(6) cells). On the other hand [125I]bPTH-(1-34) bound to ROS cells with higher affinity [dissociation constant (Kd) = 19 nM] than did [125I]bPTH-(1-84) (Kd = 210 nM). Measurements of trichloroacetic acid precipitability and analysis of rebinding of previously incubated radioligand to fresh cells ruled out degradation of the tracer as an explanation for these differences. The maximum cell cAMP response to bPTH-(1-34) (Vmax = 780 +/- 32 pmol/2 X 10(6) cells X 5 min) was reached at 10(-7) M concentration with an affinity [Michaelis-Menten constant (Km)] of 3 nM. On the other hand, the Vmax with intact bPTH-(1-84) was lower (400 +/- 7 pmol/2 X 10(6) cells X 5 min), with a Km of 60 nM). Further studies with the bPTH-(1-84) tracer showed inability of hormonal fragments to compete completely for binding. At a concentration of 3 microM, bPTH-(1-84) reduced tracer binding by 82.5%, compared to 18% by bPTH-(1-34) and 10% by (Nle8,Nle18,Tyr34)bPTH-(1-34)amide, 60% by human PTH (hPTH)-(53-84), and 70% by the combination of bPTH-(1-34) and hPTH-(53-84). hPTH-(53-84) itself did not elicit a cAMP response after 5 min or 1 h of incubation nor did it significantly alter the cAMP response of the cells to bPTH-(1-84). These studies suggest that PTH binds to ROS 17/2.8 cells by sites carboxy-terminal (C-terminal) to position 34, in addition to sites within the amino-terminal portion of the hormone molecule; 72% of the binding of intact hormone to these cells was to the C-terminal 35-84 region of the PTH molecule. The significance of the C-terminal binding sites is presently unclear, but they do not appear to be coupled to adenylate cyclase. Further work is needed to determine the effects of C-terminal PTH fragments on bone cell metabolism.

Specific immunohistochemical localization of type III collagen in porcine periodontal tissues using the peroxidase-antiperoxidase method

Specific antibodies to porcine gingival type III collagen were raised in sheep. After purification on collagen affinity columns the antibodies were used for immunohistochemical localization of type III collagen in porcine periodontal and dental tissues employing the peroxidase-antiperoxidase (PAP) procedure. The extent of staining of the periodontal tissues was found to approximate the amount of type III collagen measured biochemically. A fairly uniform distribution of type III collagen was observed in the periodontal ligament and gingiva with more intense staining often being associated with blood vessels. A regular pattern of weakly staining fibers could be demonstrated throughout the cementum and in parts of the alveolar bone tissue. In addition, occasional sites in the cementum having a different morphological appearance from the rest of the cementum exhibited bundles of positively stained fibers. Although the bone tissue was essentially unstained, fibers in the endosteal spaces stained strongly. Sharpey's fibers passing from the soft connective tissues into alveolar bone and cementum also stained strongly. Three distinct arrangements of collagen fibers stained by the type III collagen antibodies could be identified: first, a reticular pattern, which was seen at the junction of the gingival epithelium and connective tissue, and in the endosteal spaces and dental pulp; second, a more diffuse pattern of fibers intermingled with type I collagen in the soft connective tissues; and third, a coating of some Sharpey's fibers, having a core believed to be type I collagen, and of fibers in the cementum inclusions.

Human parathyroid hormone carboxyterminal peptide (53-84) stimulates alkaline phosphatase activity in dexamethasone-treated rat osteosarcoma cells in vitro

Previous studies in our laboratory have demonstrated relatively large numbers of cell surface binding sites for the carboxylterminal (53-84) region of PTH on ROS 17/2.8 rat osteosarcoma cells, a clonal osteoblast-like cell line. In order to gain insight into the significance of these carboxylterminal binding sites, we studied the effect of intact bovine PTH (1-84), its aminoterminal fragment bovine PTH (1-34), and the human PTH carboxylterminal fragment (53-84) on alkaline phosphatase activity in dexamethasone-treated rat osteosarcoma (ROS) 17/2.8 cells. While bovine PTH (1-84) and its aminoterminal 1-34 fragment inhibited alkaline phosphatase activity, we saw a dose-related stimulation of activity by human PTH (53-84), with maximal stimulation occurring after 120 hours, at a concentration of 10(-8) M. The effect was not seen in dexamethasone-untreated cells. To our knowledge, this is the first published demonstration of biological activity of this carboxylterminal PTH peptide, previously thought to be inactive. It is likely that dexamethasone caused differentiation of cells to a type more sensitive to human PTH (53-84). Further studies are necessary to elucidate the physiological significance of these findings.

The E1B 19K protein associates with lamins in vivo and its proper localization is required for inhibition of apoptosis

Expression of the E1B 19K protein is required to inhibit apoptosis induced by E1A during adenovirus infection and transformation. E1B 19K is homologous to Bcl-2 in function and the two proteins also share limited amino acid sequence homology. Consequently, the E1B 19K and Bcl-2 proteins bind to and inhibit the cellular death-inducing proteins Bax, Bak and Nbk/Bik. Both E1B 19K and Bcl-2 localize to membranes of the nucleus and the endoplasmic reticulum. In addition to membrane association, and unlike Bcl-2, the E1B 19K protein is found associated with intermediate filament proteins in the cytoplasm and the nuclear lamina and copurifies with the lamins both during infection and transformation. While a membrane targeting domain at the C-terminus of Bcl-2 ensures its proper localization, the mechanism by which the E1B 19K protein localizes is unknown. Not surprisingly, lamin A fragments were cloned from a yeast two-hybrid screen for E1B 19K-interacting proteins. The interaction was demonstrated in yeast and mammalian cells in vivo and in vitro and was unique and specific to E1B 19K, with no interaction evident between Bcl-2 and lamin A. Mutants of lamin A/C which localized inappropriately in the cytoplasm or nucleus but retained E1B 19K binding, interfered with the nuclear envelope and cytoplasmic membrane targeting of the E1B 19K protein. Improper localization impaired the ability of the E1B 19K protein to inhibit apoptosis. Thus, proper localization of the E1B 19K protein is required for its function and the interaction of the E1B 19K protein with lamin A/C may represent a means for nuclear envelope localization.

Immunohistochemical demonstration of parathyroid hormone binding to specific cell types in fixed rat bone tissue

Deparaffinized sections of fixed decalcified neonatal rat radii were incubated in bovine PTH (bPTH; 1-10 MRC units/ml) or in PTH-solvent. They were then stained for PTH by the peroxidase-antiperoxidase method using guinea pig antiserum to bPTH and the substrate 3,3'-diaminobenzidine-H2O2. Staining caused by nonspecific binding of PTH to the bone matrix and the glass slides supporting the sections was eliminated completely by preincubation of the sections in 100% normal goat serum. Cross-reactivity of the antiserum to erythrocytes was eliminated by preabsorption of the antiserum with fixed rat erythrocytes. After the cross-reactivity of the anti-PTH antiserum to erythrocyte components and the nonspecific binding of PTH to bone matrix were eliminated, we were able to demonstrate intense staining over the cytoplasm of the osteoclasts in rat radii sections incubated with PTH. Less intense staining was observed over the osteocytes, periosteal osteoblasts, and, possibly, the endosteal osteoblasts. An explanation for this differential staining could be that osteoclasts have a greater receptor number and/or a greater receptor affinity for the bPTH than do osteocytes and osteoblasts. This study demonstrates that binding of PTH to bone tissue can be localized in all identifiable osteoclasts, osteocytes, and osteoblasts, and thus suggests that all three cell types can interact directly with PTH.

Algorithms for reengineering 1991 census geography

"The availability of GIS [geographic information systems] technology and digital boundaries of census output areas now makes it possible for users to design their own census geography. Three algorithms are described that can be used for this purpose. An Arc/Info implementation is briefly outlined and case studies presented to demonstrate some of the results of explicitly designing zoning systems for use with 1991 [U.K.] census data."