Segregation of structural collagen genes in adolescent idiopathic scoliosis.

The etiology of idiopathic scoliosis remains unknown. The condition results in a characteristic deformity of the spine and surrounding tissues. Both Types I and II collagen are important constituents of the affected tissues, and thus defective collagens are reasonable candidates for the primary abnormality in adolescent idiopathic scoliosis (AIS). Direct analyses of the amount and solubility of collagen have revealed differences between normal individuals and those with AIS. However, these changes may be secondary to the mechanical effects of the spinal deformity. Segregation analysis was done of genetic markers linked to the structural genes encoding Types I and II collagen to test these candidate loci in four pedigrees with dominantly inherited AIS. In one pedigree, markers linked to both of the Type I collagen loci (COL1A1 and COL1A2) were found to be inherited independently of the abnormal phenotype. Two pedigrees were discordant at one of the Type I loci. The condition also segregated independently of the locus for Type II collagen (COL2A1) in three pedigrees. This is evidence against idiopathic scoliosis generally being caused by mutations in the Types I and II collagen genes.     

Benzo(a)pyrene inhibits epidermal growth factor binding and receptor autophosphorylation in human placental cell cultures

Studies investigated the effects of benzo(a)pyrene (BP) treatment on epidermal growth factor (EGF) receptor binding and kinase activity in human placental cell cultures. Specific binding of 125I-EGF to cells from early gestation placentae was significantly decreased by 37 and 60% following exposure to 1 and 10 microM BP, respectively, for 24 hr. In contrast, cells cultured from term placentae showed no inhibitory effect of either concentration of BP. Specific binding of 125I-labeled insulin and insulin-like growth factors-I and -II to early gestation cells was decreased only 15-18% at 10 microM BP, which indicates that loss of membrane receptors appears to be selective for EGF. Scatchard analysis of early gestation cells revealed that BP was associated with a dose-dependent loss in the number of high affinity EGF binding sites. Evidence from cross-linking and autophosphorylation experiments confirmed that the Mr 170,000 binding protein was decreased in a dose-dependent manner following BP treatment. In comparison, term placental cells exhibit a 26% loss of EGF receptor autophosphorylation without alteration in binding following exposure to 10 microM BP. Thus, early gestation cells exhibit a BP-related down-regulation of EGF receptors, whereas term placental cells show receptor desensitization. No adverse effect of BP treatment was observed on the incorporation of [35S] methionine into proteins secreted by early gestation cells. Further experiments compared the effects of BP with the related poly-cyclic compounds beta-naphthoflavone, alpha-naphthoflavone, and 3-methylcholanthrene. In early gestation cells, EGF binding and receptor autophosphorylation were measurably decreased at 10 microM concentrations of these polycyclic compounds, but to a lesser extent than observed with BP. In term placental cells, however, EGF binding was unchanged or increased, whereas receptor autophosphorylation was decreased 10-26%. Thus, exposure of term placental cells to these polycyclic compounds leads to a dissociation between EGF binding and receptor protein kinase activity. Finally, aryl hydrocarbon hydroxylase activity was induced 20- to 200-fold in early placental cells exposed to BP, beta-naphthoflavone, and 3-methylcholanthrene. In summary, the direct effects of BP and related compounds observed on placental EGF receptors may indicate altered function of EGF in the regulation of cell growth and differentiation in the human placenta.     

Midazolam: kinetics and effects on memory, sensorium, and haemodynamics.

This study aimed not only to compare the pharmacokinetics of oral and intravenous doses of the new water-soluble benzodiazepine, midazolam, but also to study the effects on haemodynamics, sensorium, and memory performance. Eight normal human volunteers each received a single 15 mg dose of midazolam base orally and intravenously in randomized sequence 2 weeks apart. Serial venous samples were obtained for 12 h after dosing. Vital signs, sensorium testing and memory testing using word lists were also performed. Computerized non-linear least squares curve-fitting of the two-compartment open model to the oral and intravenous data simultaneously yielded the following estimates: V1, 0.33 1 kg-1, VdSS, 1.08 1 kg-1, t1/2,lambda, 0.10 h, t1/2,Z, 1.89 h, ka 1.17 h-1 and bioavailability, 49%. The intravenous dose decreased the systolic pressure 22 mm Hg during the first half-hour and the oral dose had 50% less effect. Most subjects became drowsy halfway through the infusion and were only rousable to voice by its end. The sensorium was clear by 2-3 h. After oral dosing the peak sensorium effects of ataxia-dysarthria were seen at 30 min and had cleared by 2 h. Memory testing showed that memory acquisition was markedly impaired for at least 90 min after the intravenous dose and slight recovery was apparent at this time after the oral dose. Memory performance was proportionately more impaired than the sensorium score. We conclude that: midazolam kinetics are characterized by rapid absorption, but incomplete bioavailability and rapid elimination, midazolam intravenously may lower blood pressure significantly, and the level of consciousness correlates poorly with the degree of memory impairment.     

Tumor osteolysis in osteopetrotic mice

Details of the cellular and biochemical mechanisms involved in focal destruction of bone at sites of tumor osteolysis are unknown. It has been shown that tumors from sarcoma (2472) cell lines induce focal osteolysis in mice by stimulating formation and activation of osteoclasts. In this report, the influence of 2472 tumors on the skeletons of osteoclast-deficient animals (op/op) was studied. After op/op femora had been inoculated with 2472 cells, tumors developed and focal osteolysis occurred. There were more osteoclasts per histologic section in sham-injected femora (19 ± 5) than in tumor-bearing femora (412 ± 129) (p < 0.05). The size of the osteoclasts also increased from 304 ± 81 μm² in sham-injected limbs to 407 ± 62 μm² in tumor-bearing limbs (p < 0.001). Conditioned media from 2472 op/op tumor explants contained macrophage colony-stimulating factor. A deficiency of osteoclasts in op/op mice is the result of the absence of this factor; therefore, these data introduce the possibility that macrophage colony-stimulating factor derived from 2472 tumor may be responsible for directing osteoclast-mediated osteolysis at sites of the tumor.