Loma Linda University

About: Loma Linda University is a education organization based out in Loma Linda, California, United States. It is known for research contribution in the topics: Population & Medicine. The organization has 9220 authors who have published 13485 publications receiving 447094 citations. The organization is also known as: University of Loma Linda.

Connective tissue regeneration to periodontally diseased teeth. A histological study.

Abstract: A study was made to investigate the biological principle of new attachment of connective tissue to periodontally diseased root surfaces utilizing the previous finding that topical application of citric acid to the affected area may stimulate periodontal regeneration. Reconstructive surgery was performed on ten surfaces of nine teeth involved in advanced chronic periodontal disease. A muco-periosteal flap was raised and the apical extent of existing subgingival calculus was demarcated by a notch made through the calculus and into the root. Following thorough instrumentation, a saturated solution of citric acid was applied to the root surface for five minutes and the flap repositioned and sutured. Four months later the teeth with attached periodontal tissues were removed and processed for histological analysis. Connective tissue regeneration characterized by deposition of new cementum, and more coronally, by tightly apposed soft connective tissue had occurred in all specimens. The junctional epithelium ended 1.2–2.6 mm coronal to the apical border of the notch in the various specimens. The results demonstrate that regeneration of periodontal tissues to a root surface that has become denuded as a result of chronic, destructive periodontal disease and that has been covered by calculus is, in fact, a biological possibility. This study does not establish whether or not acid conditioning of the root surface is a prerequisite for new attachment.

Phosphotyrosyl protein phosphatases.

Abstract: Enzyme-catalysed reversible protein phosphorylation is an important cellular regulatory mechanism (Nimmo & Cohen, 1977; Krebs & Beavo, 1979). Regulatory protein phosphorylation occurs most frequently on seryl and threonyl residues (Taborsky, 1974), and less frequently, on tyrosyl residues (Hunter, 1982). Protein phosphotyrosine [Tyr(P)] normally accounts for only 0.01-0.050o of the total protein phosphoamino acid content of a normal cell (Hunter & Sefton, 1980), but this value increases to 1-3 when the cells are infected with viruses (Sefton et al., 1981; Martensen, 1982). In the last several years much attention has been focused on the phosphotyrosyl phosphorylation of cellular proteins by specific phosphotyrosyl kinases, and phosphotyrosyl phosphorylations have been associated with the regulation of cellular activities, including proliferation, differentiation, and transformation (Hunter & Sefton, 1982; Heldin & Westermark, 1984; Sefton & Hunter, 1984; Swarup et al., 1984; Sefton, 1985; Coughlin et al., 1988). The suggested association between phosphotyrosyl phosphorylation and cell proliferation was further supported by studies which showed that a number of polypeptide growth factor receptors [i.e. epidermal growth factor (EGF), platelet-derived growth factor, insulin-like growth factor-i, insulin, etc.] possess intrinsic phosphotyrosyl kinase activities that are activated when the growth factors are bound, and that the activation of the receptor phosphotyrosyl kinases is essential for the action of the growth factors (Cohen et al. 1980; Ek et al., 1982; Jacobs et al., 1983; Reynolds et al., 1981; Sefton & Hunter, 1984; Gammeltoft & Van Obberghen, 1986). Moreover, many oncogene products also act as phosphotyrosyl kinases, and share extensive sequence homology with several polypeptide growth factor receptors (Heldin & Westermark, 1984; Sefton, 1985; Pimental, 1987). Studies using site-directed mutagenesis (Chou et al., 1987; Kmiecik & Shalloway, 1987) and specific anti-(receptor phosphotyrosyl kinase) antibodies (Morgan et al., 1986; Morgan & Roth, 1987) have indicated that the phosphotyrosyl kinase activity of growth factor receptors is an essential component for the biological action of the growth factors and of the transforming proteins (Kmiecik & Shalloway, 1987). Together, these observations have led to the general conclusion that increased cellular phosphorylation of protein tyrosyl residues plays an important role in the action of growth factors and also serve to regulate the cellular growth processes in general (Hunter & Cooper, 1983). In order for phosphotyrosyl phosphorylation system to serve an important physiological regulatory mechanism, the process must be reversible [i.e. a process for removing the phosphate (Pi) from the phosphotyrosyl residues must exist]. The enzyme activities responsible for dephosphorylating phosphotyrosyl proteins are known as phosphotyrosyl protein phosphatases (PTPP). If phosphotyrosyl phosphorylation represents a general physiological regulatory mechahnism, it is reasonable to expect that the overall phosphQtyrosyl phosphorylation levels in cells are regulated by the balance of the activities of both phosphotyrosyl kinases and PTPPs. Thus, to achieve a complete understanding of the significance of this reversible enzymic covalent modification, it is necessary to know the nature and the regulation of, not only phosphotyrosyl kinases, but also PTPPs. The enzymology of phosphotyrosyl kinases has been intensively investigated (Brugge & Chinkers, 1983) and extensively reviewed (Sefton & Hunter, 1984; Hunter & Cooper, 1985; Sefton, 1985). However, relatively little is known of the nature of the PTPPs (Foulkes, 1983). Consequently, we will focus this review on the current status of our understanding of the nature and regulation of the PTPP activities. We will also summarize the recent evidence suggesting a physiological role for PTPP activity in the regulation of normal bone cell growth.

Tamoxifen Inhibits Osteoclast-Mediated Resorption of Trabecular Bone in Ovarian Hormone-Deficient Rats*

Abstract: The effects of the nonsteroidal antiestrogen tamoxifen were determined on trabecular bone mass in the proximal tibial metaphysis of intact and ovariectomized rats. Rats were ovariectomized at the beginning of the study. On day 7 of the study, 5-mg slow release pellets of tamoxifen or placebo were implanted sc. All of the rats were killed on day 28 of the experiment. Sections of the proximal tibial metaphysis were stained for acid phosphatase and evaluated histomorphometrically. Ovariectomy resulted in marked loss of bone. Compared to the values in sham-operated animals, the trabecular bone at a sampling site in the secondary spongiosa of ovariectomized rats was reduced by more than 60%, the length of trabecular bone surface covered by osteoclasts was increased by 563%, the percentage of trabecular bone surface covered by osteoclasts was increased by 567%, the mean osteoclast size was increased by 84%, and the number of nuclei per osteoclast was increased by 38%. In contrast, treatment of ovariectomized rats for 3 weeks with tamoxifen restored the histomorphometric measurements to values comparable to those in sham-operated animals. 17 beta-Estradiol increased trabecular bone fractional area in ovariectomized and sham-operated rats, and administration of tamoxifen to estrogen-treated, ovariectomized, and sham-operated animals produced a further increase in trabecular bone. In summary, 1) ovariectomy resulted in large increases in both the number and activity of osteoclasts, 2) the increased bone resorption associated with ovariectomy produced a net loss of trabecular bone, and 3) treatment of ovariectomized rats with tamoxifen prevented these skeletal changes. The results indicate that in the rat, tamoxifen mimics the effects of estrogen on trabecular bone at concentrations that are not uterotropic.

Male Oxidative Stress Infertility (MOSI): Proposed Terminology and Clinical Practice Guidelines for Management of Idiopathic Male Infertility

Abstract: Despite advances in the field of male reproductive health, idiopathic male infertility, in which a man has altered semen characteristics without an identifiable cause and there is no female factor infertility, remains a challenging condition to diagnose and manage. Increasing evidence suggests that oxidative stress (OS) plays an independent role in the etiology of male infertility, with 30% to 80% of infertile men having elevated seminal reactive oxygen species levels. OS can negatively affect fertility via a number of pathways, including interference with capacitation and possible damage to sperm membrane and DNA, which may impair the sperm's potential to fertilize an egg and develop into a healthy embryo. Adequate evaluation of male reproductive potential should therefore include an assessment of sperm OS. We propose the term Male Oxidative Stress Infertility, or MOSI, as a novel descriptor for infertile men with abnormal semen characteristics and OS, including many patients who were previously classified as having idiopathic male infertility. Oxidation-reduction potential (ORP) can be a useful clinical biomarker for the classification of MOSI, as it takes into account the levels of both oxidants and reductants (antioxidants). Current treatment protocols for OS, including the use of antioxidants, are not evidence-based and have the potential for complications and increased healthcare-related expenditures. Utilizing an easy, reproducible, and cost-effective test to measure ORP may provide a more targeted, reliable approach for administering antioxidant therapy while minimizing the risk of antioxidant overdose. With the increasing awareness and understanding of MOSI as a distinct male infertility diagnosis, future research endeavors can facilitate the development of evidence-based treatments that target its underlying cause.