Time-dependent degradation of titanium osteoconductivity: An implication of biological aging of implant materials

The shelf life of implantable materials has rarely been addressed. We determined whether osteoconductivity of titanium is stable over time. Rat bone marrow-derived osteoblasts were cultured on new titanium disks (immediately after acid-etching), 3-day-old (stored after acid-etching for 3 days in dark ambient conditions), 2-week-old, and 4-week-old disks. Protein adsorption capacity, and osteoblast migration, attachment, spread, proliferation and mineralization decreased substantially on old titanium surfaces in an age-dependent manner. When the 4-week-old implants were placed into rat femurs, the biomechanical strength of bone–titanium integration was less than half that for newly processed implants at the early healing stage. More than 90% of the new implant surface was covered by newly generated bone compared to 58% for 4-week-old implants. This time-dependent biological degradation was also found for machined and sandblasted titanium surfaces and was associated with progressive accumulation of hydrocarbon on titanium surfaces. The new surface could attract osteoblasts even under a protein-free condition, but its high bioactivity was abrogated by masking the surface with anions. These results uncover an aging-like time-dependent biological degradation of titanium surfaces from bioactive to bioinert. We also suggest possible underlying mechanisms for this biological degradation that provide new insights into how we could inadvertently lose, and conversely, maximize the osteoconductivity of titanium-based implant materials.     

The effect of ultraviolet functionalization of titanium on integration with bone

Titanium implants are used as a reconstructive anchor in orthopedic and dental diseases and problems. Recently, ultraviolet (UV) light-induced photocatalytic activity of titanium has earned considerable and broad interest in environmental and clean-energy sciences. This study determines whether UV treatment of titanium enhances its osteoconductive capacity. Machined and acid-etched titanium samples were treated with UV for various time periods up to 48 h. For both surfaces, UV treatment increased the rates of attachment, spread, proliferation and differentiation of rat bone marrow-derived osteoblasts, as well as the capacity of protein adsorption, by up to threefold. In vivo histomorphometry in the rat model revealed that new bone formation occurred extensively on UV-treated implants with virtually no intervention by soft tissue, maximizing bone–implant contact up to nearly 100% at week 4 of healing. An implant biomechanical test revealed that UV treatment accelerated the establishment of implant fixation 4 times. The rates of protein adsorption and cell attachment strongly correlated with the UV dose-responsive atomic percentage of carbon on TiO₂, but not with the hydrophilic status. The data indicated that UV light pretreatment of titanium substantially enhances its osteoconductive capacity, in association with UV-catalytic progressive removal of hydrocarbons from the TiO₂ surface, suggesting a photofunctionalization of titanium enabling more rapid and complete establishment of bone–titanium integration.     

Long‐term follow‐up of patients with hepatitis C with a normal alanine aminotransferase

An attempt was made to identify factors influencing the cumulative probability of an increased alanine aminotransferase (ALT) level and hepatocarcinogenesis in hepatitis C patients with a normal ALT level initially. A total of 398 consecutive patients with a normal ALT level initially for 6 months or more and follow‐up period longer than 3 years during the period January 1995 to December 2004 were included. Patients were classified by ALT level into three groups: Group A (3–20 IU/L), Group B (21–30 IU/L), and Group C (31–35 IU/L). Factors associated with the cumulative probability of increased ALT level and hepotocarcinogenesis were evaluated. Women in groups B and C and men in Group C showed high cumulative probabilities of increased ALT levels. Factors associated with increased ALT were a high ALT level (Group B, relative risk; 1.758 [95% confidence interval: 1.290–2.392], P < 0.001, Group C, 3.328 [2.256–4.909], P < 0.001), high lactate dehydrogenase level (2.352 [1.445–3.829], P = 0.001), or low total cholesterol level (1.957 [1.330–2.882], P = 0.001). Factors associated with incidence of hepatocellular carcinoma were increased age (3.088 [1.025–9.308], P = 0.045), high ALT level (Group C, 5.803 [1.530–22.066], P = 0.010), and high total bilirubin level (8.309 [2.235–30.888], P = 0.002). In patients with hepatitis C with a normal ALT level initially, an ALT level of 21–35 IU/L is a risk factor for an increased ALT level and hepatocarcinogenesis. J. Med. Virol. 81:446–451, 2009. © 2009 Wiley‐Liss, Inc.     

N-Acetyl cysteine prevents suppression of oral fibroblast function on poly(methylmethacrylate) resin

Despite the proven cytotoxicity, poly(methylmethacrylate) (PMMA) resin is one of the most frequently and extensively used materials in medical and dental fields. The study examined the potential detoxification of the resin material and restoration of the resin-induced suppression of cellular function using an antioxidant amino acid derivative, N-acetyl cysteine (NAC). Oral fibroblasts extracted from rat oral mucosa were cultured on the resin material with or without incorporation of NAC into the material. Twenty-four hour after incubation, less than 2% of the cells were viable on the untreated control resin, while up to 35% of the cells were viable on the resin with incorporation of NAC. At day 7 of culture, the expression of collagen I and III genes was downregulated on the untreated resin, while the cells on NAC-supplemented resin showed the expression levels similar to those in polystyrene culture. The cells produced three times greater amount of collagen on the NAC-supplemented resin than on the untreated resin. The data demonstrated that the cytotoxicity of PMMA resin was substantially lower when the material contains NAC. The potential usefulness of this principle should be explored with a view of developing biocompatible polymer-based materials in a broad range of dental and medical resin materials and tissue engineering scaffolds.     

Chemodynamics underlying N-acetyl cysteine-mediated bone cement monomer detoxification

Methyl methacrylate (MMA)-based bone cement monomer is cytotoxic. N-Acetyl cysteine (NAC), a cysteine derivative, may alleviate this toxicity by inactivating the monomer components with its sulfhydryl moiety. This study examined the chemical interaction dynamics between bone cement monomer and NAC resulting in detoxification of the monomer. A monomer/NAC mixture was prepared by mixing and incubating a commercially available MMA-based bone cement monomer with NAC for various time periods of 1 min, 1 h, 6 h and 24 h. Rat bone marrow-derived osteoblastic cells were cultured with either the monomer/NAC mixture or the monomer alone. Only 17% of the cells were viable 24 h after seeding in the culture containing the monomer alone. The proliferation rate and alkaline phosphatase activity of the cells were substantially reduced under this condition. In contrast, when cultured with the monomer/NAC mixture, the viability and function of the cells were improved with increasing time of monomer/NAC incubation. For instance, the monomer/NAC mixture that was pre-reacted for 1 min increased cell viability from 17% to 55%. The monomer/NAC mixture that was pre-reacted for 24 h nearly completely restored cell viability, proliferation and ALP activity to the level of an untreated control culture. The DPPH radical-scavenging capacity of monomer/NAC mixture decreased with an increase in their reaction time, indicating time-dependent depletion of the NAC anti-oxidant moiety. Within the limit of this experimental condition, these data demonstrate the immediate initiation and rapid completion of bone cement monomer/NAC interaction, resulting in abrogation of the monomer’s cytotoxicity.     

The dorsomedial hypothalamic nucleus is not necessary for food-anticipatory circadian rhythms of behavior, temperature or clock gene expression in mice

Circadian rhythms in mammals are regulated by a light-entrainable circadian pacemaker in the hypothalamic suprachiasmatic nucleus and food-entrainable oscillators located elsewhere in the brain and body. The dorsomedial hypothalamic nucleus (DMH) has been proposed to be the site of oscillators driving food-anticipatory circadian rhythms, but this is controversial. To further evaluate this hypothesis, we measured clock gene, temperature and activity rhythms in intact and DMH-ablated mice. A single 4-h midday feeding after an overnight fast induced mPer1 and mPer2 mRNA expression in the DMH, arcuate nucleus, nucleus of the solitary tract and area postrema, and reset daily rhythms of mPer1 , mPer2 and mBMAL1 in the DMH, arcuate and neocortex. These rhythms persisted during 2 days of food deprivation after 12 days of scheduled daytime feeding. Acute induction of DMH mPer1 and mPer2 was N -methyl- d -aspartate (NMDA) receptor-dependent, whereas rhythmic expression after 6 days of restricted feeding was not. Thermal DMH lesions did not affect acute induction or rhythmic expression of clock genes in other brain regions in response to scheduled daytime feeding. DMH lesions attenuated mean daily activity levels and nocturnality but did not affect food-anticipatory rhythms of activity and body temperature in either light–dark or constant darkness. These results confirm that the DMH and other brain regions express circadian clock gene rhythms sensitive to daytime feeding schedules, but do not support the hypothesis that DMH oscillations drive food-anticipatory behavioral or temperature rhythms.     

Mutant γPKC found in spinocerebellar ataxia type 14 induces aggregate-independent maldevelopment of dendrites in primary cultured Purkinje cells

Missense mutations in protein kinase Cγ (γPKC) gene have been found in spinocerebellar ataxia type 14 (SCA14), an autosomal dominant neurodegenerative disease. We previously demonstrated that mutant γPKC found in SCA14 is susceptible to aggregation and induces apoptosis in cultured cell lines. In the present study, we investigated whether mutant γPKC formed aggregates and how mutant γPKC affects the morphology and survival of cerebellar Purkinje cells (PCs), which are degenerated in SCA14 patients. Adenovirus-transfected primary cultured PCs expressing mutant γPKC-GFP also had aggregates and underwent apoptosis. Long-term time-lapse observation revealed that PCs have a potential to eliminate aggregates of mutant γPKC-GFP. Mutant γPKC-GFP disturbed the development of PC dendrites and reduced synapse formation, regardless of the presence or absence of its aggregates. In PCs without aggregates, mutant γPKC-GFP formed soluble oligomers, resulting in reduced mobility and attenuated translocation of mutant γPKC-GFP upon stimulation. These molecular properties of mutant γPKC might affect the dendritic morphology in PCs, and be involved in the pathogenesis of SCA14.     

Clinical practice and research activities for early psychiatric intervention at Japanese leading centres

Aim: To describe clinical practice and research activities for early psychiatric intervention in Japan, a country with a huge number of psychiatric beds and a history of long‐stay, hospital‐based psychiatry. Methods: The characteristics, methods and activities of early intervention studies and implementation at four leading institutions in Japan are described. Results: The Tokyo Youth Club (Tokyo), the Department of Neuropsychiatry of Toyama University Hospital (Toyama), the S endai A t‐risk Mental State and F irst E pisode (SAFE) service (Sendai), and the Il Bosco of Toho University Omori Medical Center (Tokyo) have unique and active psychiatric programmes. Eachcentre has its own clinical research programme and treatment strategies. The Japanese Society for the Prevention of Psychiatric Disorders, founded in 1996, has made a steady contribution to psychiatric care by providing a forum for members to promote best practices for early intervention and by hosting annual meetings to discuss research and treatment. Conclusions: The Japanese psychiatry service is continuing its transition from hospital‐based psychiatry to community‐based psychiatry. Despite these difficult circumstances, the publication of data on the duration of untreated psychosis in Japan along with evidence that early detection determines outcome has encouraged new attempts to promote early psychiatric intervention.     

A case of pathological complete response after treatment with uracil/tegafur (UFT) and folinate (Leucovorin) for liver metastasis of colon cancer

The patient is a 62-year-old female who underwent a right hemicolectomy for type-2 ascending colon cancer (moderately-differentiated adenocarcinoma, ss, n0, H0, P0, M0, stage II). Six months after the surgery, a solitary metastatic focus was expressed in the liver S3. Because schizophrenia was present concurrently, tegafur and uracil/folinate (UFT/Leucovorin) treatment was selected and performed for 3 months. Because the tumor shrank afterward, a partial hepatectomy was performed to obtain a curative resection. In a pathological examination of the resected focus, cicatricial/necrotic findings were observed, but no cancer cells were observed; hence, it was determined to be a pathological complete response (CR). In regard to chemotherapy for distant metastasis of colorectal cancer, many molecular-targeted agents are being introduced, thus resulting in more treatment options; however, depending on the patient's background, UFT/LV treatment can be an effective treatment option.