Bone density patterns after normal and premature menopause

Objectives: The investigation of the effect of time and type of menopause on bone mineral density (BMD) at different ages. Methods: Five hundred and fourteen women, who had never received any hormonal substitution were studied in a cross-sectional design: 177 with normal (NMP), 210 with surgical (SUMP) and 127 with premature natural (EMP) menopause. Age at menopause was 49.1±3.9, 38.3±4.7 and 38.1±4.2 years (mean±1 S.D.), respectively. BMD was measured at L2–L4 vertebrae and proximal femur by the DEXA method. Results: EMP women presented significantly lower vertebral BMD than NMP women in the 45–55-years segments (P<0.001), but did not differ from SUMP women. This group exhibited lower vertebral BMD than NMP between 45 and 50 years (P<0.001). Regarding femoral neck, EMP women exhibited lower values than SUMP in the 45–50 and 55–65 age segments (P<0.001) whereas SUMP women presented significantly higher BMD values than NMP women after 55 years of age (P<0.001). The percentages of women with vertebral BMD (T-score values) in the osteoporotic range were significantly greater in EMP compared with either NMP or SUMP groups (both P<0.001) whereas in femoral neck lower in SUMP than the other two categories. Conclusions: Women with either natural or surgical premature menopause exhibit lower BMD of trabecular bone compared with normal menopause women at the age segments 45–55 and 45–50, respectively. However, surgical menopause women exceed normal menopause women in their mixed bone BMD values after 60 years as well as premature natural menopause women at almost all age segments.     

Effect of long‐term depletion of plasma methionine on the growth and survival of human brain tumor xenografts in athymic mice

Depletion of plasma methionine is expected to inhibit or reverse growth of methionine‐dependent tumors; however, modulation of methionine and other sulfur amino acids is not a trivial task in experimental animals. l‐Methioninase from Pseudomonas putida at 1,000 U/kg causes acute reduction of plasma methionine by 80% in mice, but recovery occurs within 14 hours. Restriction of dietary choline and replacement of dietary methionine with homocystine results in 50% chronic reduction of plasma methionine. A >70% reduction can be accomplished with a diet deficient in methionine, homocystine, and choline, but ultimately this diet is lethal. Plasma methionine can be lowered to a steady state of <5 μM in mice with a combination of dietary restriction of methionine, homocysteine, and choline and synchronous treatments with intraperitoneal injections of 1,000 U/kg L‐methioninase and 25–50 mg/kg homocystine, each administered at 12‐hour intervals. Modulation of plasma methionine by this means causes no weight loss or pathologies in liver or pancreas, and it does not markedly alter levels of cysteine, homocysteine, or glutathione in plasma or in hepatic tissue. When this procedure is applied to athymic mice bearing human medulloblastoma (Daoy) tumors subcutaneously, tumor growth is inhibited. Methionine deprivation arrests mitosis by blocking the cell cycle in G2 and induces apoptosis. Tumor stasis was achieved in 100% of treated animals within 4 days of treatment, and regression was seen in one‐third of animals after a 10‐day period. These data strongly support the use of methionine‐depleting regimens for tumor treatments.     

Metabolic response of normal and malignant tissue to acute and chronic methionine stress in athymic mice bearing human glial tumor xenografts

Chronic methionine (MET) stress, defined as depletion of plasma MET to levels below 5 microM, can be induced in animals with withdrawal of dietary MET, homocysteine (HCYS), and choline (CHOL) plus periodic administration of recombinant L-methionine-alpha-deamino-gamma-lyase (rMETase) and rescue homocystine (HCYSS), given i.p. every 8 and 24 h, respectively. This study describes the effect of this MET depleting regimen (METdr) on normal and malignant tissue using athymic mice bearing human glial tumor xenografts. A 7-day METdr in athymic mice bearing SWB40 and U87 anaplastic astrocytoma xenografts reduced tumor MET to 30% of their baseline values. Although this reduction halted tumor growth, it did not induce the expected complete inhibition of mitosis or a rapid and extensive necrosis. In contrast, SWB77 and D-54 xenografts (glioblastomas) showed marked regression, widespread necrosis, and complete loss of mitotic activity when they were subjected to METdr. Levels of MET in SWB77 and D-54 did not respond to METdr as readily as those in SWB40 and U87 and remained relatively high as the tumor responded to treatment and regressed. High steady states of MET along with the absence of HCYS in high-grade gliomas indicates that transmethylation reactions may be inhibited in such tumors under modest methionine stress conditions. On the basis of these results, it is postulated that METdr in its present formulation is more effective against high-grade, more aggressive gliomas, which are resistant to chemotherapy, than against the more differentiated astrocytic tumors. This may be due to the higher requirements of high-grade gliomas for MET to maintain a state of active proliferation. Further studies are needed to identify the source of MET in glial tumors under METdr and to develop more effective regimens to deplete tumor MET, which might result in a complete and sustained regression of high-grade gliomas.     

Eradication of human medulloblastoma tumor xenografts with a combination of O6-benzyl-2'-deoxyguanosine and 1,3-bis(2-chloroethyl)1-nitrosourea.

O6-Benzyl-2'-deoxyguanosine (dBG), a water-soluble inhibitor of O6-methylguanine-DNA methyltransferase (MGMT), potentiates the efficacy of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) against MGMT-positive, BCNU-resistant Daoy human medulloblastoma tumor xenografts in athymic mice (S. C. Schold et al., Cancer Res., 56: 2076-2081, 1996). Such potentiation was comparable to that observed for O6-benzylguanine, the prototype MGMT inhibitor that is currently undergoing clinical trials. In this study, we optimized the therapeutic effect of the dBG and BCNU combination against brain tumor xenografts without inducing substantial toxicity in the host by adjusting the doses of both compounds. dBG was escalated from 133 mg/m2 to 200 and 300 mg/m2, whereas corresponding doses of BCNU were reduced from 25 mg/m2 to 17 and 11 mg/m2, respectively. The growth delays of 30.2, 38.4, and 22.3 days, respectively, observed for the above regimens suggest that the optimal drug combination is not achieved with maximum doses of dBG. In fact, the highest doses of dBG (300 mg/m2) contributed to more frequent BCNU-related toxicities, despite the reduced BCNU dosage, and a reduction of the therapeutic effect. Toxicity was related to the depletion of MGMT activity in the gut of host mice and was manifested by edema, inflammation, and hemorrhage in the bowel wall by subsequent BCNU administration. With additional dosage adjustments, we found that tumor suppression of >90 days without toxicity was observed at 200 mg/m2 dBG and 23 mg/m2 BCNU. At these doses, tumors were eradicated (regressed to an undetectable size for >90 days) in 8 of 12 animals. Thus, dBG is the first of the MGMT inhibitors to show a curative effect in combination with BCNU against a human central nervous system tumor xenograft in athymic mice.     

Enhancement of N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine-induced tumorigenesis in Sprague-Dawley rats by orotic acid

The effect of orotic acid (OA) on the carcinogenicity of N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) in rats was evaluated. A group of 5 week old Sprague-Dawley male rats were placed on a synthetic 20% protein diet containing 1% OA. A second group was placed on a regular, OA-free diet of similar composition. Approximately 2 weeks later, animals from both groups grown to 100 g were treated with 400 mg/kg HPOP delivered continuously for 14 days via 2002 Alzet osmotic pumps implanted s.c. Rats fed the OA diet were kept under this diet for 13 weeks following initiation of HPOP treatment and subsequently were placed on the regular diet for another 12 weeks, at which time they were killed. In the absence of OA, HPOP-treated rats developed adenomas in the kidney and lungs at incidences of 5 and 33% respectively, while pancreas and liver were unaffected. On the other hand, rats fed the OA diet and treated with HPOP developed renal mesenchymal tumors and pulmonary adenomas at incidences of 70 and 65% respectively. In addition, HPOP induced cystic lesions in the pancreas of animals fed the OA diet. The enhancement of the tumorigenic effectiveness of HPOP was at least partly ascribed to the effect of OA treatment on the rate by which carcinogen-induced alkylation of DNA was repaired in various tissues. Accumulation of N7-methylguanine in kidney, lung and pancreas of rats fed the OA diet was 1.6, 1.9 and 2.4 times higher than in respective organs of animals fed the regular diet. Similarly, concentrations of the premutagenic O6-methylguanine (O6-MeG) were 3.0, 3.1 and 2 times greater in the kidney, lung and pancreas of rats fed the OA diet than in the respective organs of those fed the regular diet. Feeding an OA diet to HPOP-treated rats did not have an effect on either the resistance of the liver to this carcinogen or on the level of O6-MeG accumulation in the DNA of this tissue.     

Intraoperative complications using the Bio-Transfix femoral fixation implant in anterior cruciate ligament reconstruction

The use of biodegradable Transfix femoral fixation technique is a safe and well-accepted method when performing anterior cruciate ligament reconstruction. We report on three cases of deformation and back out of the Bio-Transfix implant over the lateral, distal femoral cortex, with failure of the passing wire when advancing the graft into the femoral tunnel in one of these patients. Two of the patients presented with symptoms of iliotibial band friction syndrome, while the third patient was asymptomatic. The graft had clinically integrated demonstrating AP and rotational stability. The symptoms relieved after removal of the failed Bio-Transfix implants in the symptomatic patients. The aetiology of the implant failure and the alternative methods to avoid such complications are discussed.     

Isolated giant mesenteric fibromatosis (intra-abdominal desmoid tumors). Case report

A rare case of isolated giant mesenteric fibromatosis is presented. The tumor originated from the fibrous mesenteric tissue. The patient underwent laparotomy because of abdominal discomfort and sub-occlusive symptoms due to the giant mass. Differential diagnosis of mesenteric masses is discussed and the Authors also review the literature concerning this rare disease.