Oxygen transport through methacrylate-based hydrogels with potential biological capability

The permeability to oxygen of hydrogels prepared from copolymers of 2-hydroxymethyl methacrylate and p-methacryloxyl-oxyacetanilide have been studied by using an oxygen electrode in combination with a permeometer. The transmissibility Dk/L and the permeability Dk (where D, k and L are, respectively, the diffusion coefficient, the Henry constant and the thickness of the hydrogel) are measured by a combination of steady state and transitory state measurements. Both transport coefficients increase with the water content, which in turn depends on the copolymer composition. The values of these quantities tend toward a limiting value for water-saturated hydrogels. The ratio of the characteristic volume for diffusion of the oxygen molecule to the free volume of water per mole water is found to be in the vicinity of 0.10, and this value increases slightly as the fraction of the hydrophilic comonomer in the hydrogel increases. A detailed comparison of the biogels studied with six commercial contact lenses has also been performed.     

Specific selection of deoxycytidine kinase mutants with tritiated deoxyadenosine

We have shown previously that a low concentration of tritiated deoxyadenosine, i.e., 1 microCi/ml, selectively kills wild-type S49 murine lymphoma cells. Mutant cells resistant to [3H] deoxyadenosine lacked adenosine kinase completely but retained a significant level of deoxyadenosine phosphorylating activity. To study further the specificity of [3H] deoxyadenosine selection, lymphoma cell clones resistant to 15 microCi/ml [3H] deoxyadenosine have been derived. The resistant line, S49-dA15, is also resistant to high levels of nonradioactive deoxyadenosine and to deoxyguanosine but remains sensitive to thymidine. The thymidine inhibition of the growth of the mutant, in contrast to that of the wild-type cells, cannot be prevented by deoxycytidine. The mutant line lacks deoxycytidine kinase that also phosphorylates deoxyadenosine. In addition, the mutant cells excrete a large amount of deoxycytidine into culture medium, consistent with a failure of salvage of the nucleoside in the absence of an appropriate kinase, i.e., deoxycytidine kinase. In contrast, a deoxycytidine kinase-deficient cell line that was selected with arabinosylcytosine does not excrete deoxycytidine and contains high deoxycytidine deaminase activity. [3H] Deoxyadenosine can be used as a selective agent for specific selection of deoxycytidine kinase-negative mutants.     

Macrophages resistant to endogenously generated nitric oxide-mediated apoptosis are hypersensitive to exogenously added nitric oxide donors: dichotomous apoptotic response independent of caspase 3 and reversal by the mitogen-activated protein kinase kinase (MEK) inhibitor PD 098059

Nitric oxide (NO) induction through the inducible NO synthase has been demonstrated to cause cell death in macrophages. We demonstrate that, in macrophages that have been rendered resistant to apoptosis induced by inducible NO synthase (RES cells), exposure to exogenous NO donors results in a hypersensitive apoptosis reaction when compared with the parental RAW 264.7 cells. The apoptosis induced via exogenous NO donors was found to be caspase 3-independent. Although caspase 3 activity was stimulated in the apoptotic macrophages, inhibition of caspase 3 by the inhibitor DEVD-CHO (N-acetyl-Asp-Glu-Val-Asp-aldehyde) did not reverse the apoptosis induced by the NO donor S-nitrosoglutathione (GSNO). This suggests that although caspase 3 activity is stimulated during apoptosis in macrophages, this signal is not sufficient to induce apoptosis. Cleavage of the enzyme poly(ADP ribose) polymerase mirrors our results of the caspase activity. Interestingly, we show that exogenous NO donation results in an accumulation of cells at the G2/M-phase border. Here, we demonstrate that the mitogen activated protein kinase kinase (MEK) inhibitor PD 098059 can be used to reverse the G2/M-phase block and show that this treatment also inhibits the observed apoptosis in RES macrophages. Treatment with the MEK inhibitor also reversed both the caspase 3 activity and poly(ADP ribose) polymerase cleavage in cells treated with GSNO. This result indicates that the mitogen-activated protein kinase pathway may be involved in regulation of the caspase cascade. Alternatively, it may suggest an activity for the MEK inhibitor heretofore not observed, that of a cyclin kinase inhibitor. Our results suggest that selection of macrophages by resistance to endogenously generated NO may cause hypersensitivity to exogenous NO donors. These findings have relevant implications for the treatment of apoptotic-resistant cell populations that may occur in both cancer and atheroma.     

Nasopharyngeal Castleman's disease

A 19-year-old male was admitted to our clinic because of nasal obstruction and intermittent postnasal drip of 3 to 4 years' duration. Physical examination revealed a wide-based, smooth-surfaced nasopharyngeal tumor which was suspected to be a nasopharyngeal angiofibroma after examination of computed tomographic scans and an angiogram. However, after the tumor was removed by surgical excision via a transpalatal approach, the pathologic examination revealed Castleman's disease of the hyaline-vascular type. There was neither evidence of recurrence nor nasal problems at 4 years' follow-up. To our knowledge, Castleman's disease, or angiofollicular lymph node hyperplasia, may present as a local or generalized tumor-like condition, usually in the chest or abdomen, and may involve both the lymph nodes and non-nodal tissues. A review of previous articles reveals that there has not been any report of Castleman's disease found in the nasopharynx. This rare disorder is presented and discussed.     

Correlation of nicotinic binding with neurochemical markers in Alzheimer's disease

The loss of neocortical synapses that occurs in Alzheimer's disease (AD) has been shown to correlate with cognitive decline. In addition, marked losses in the cholinergic system in AD, specifically choline acetyltransferase (ChAT) activity and high affinity presynaptic neuronal nicotinic cholinergic receptors (nAChRs), have also been described. We hypothesized that in AD, the loss of [3H]-ligand binding to nAChRs, which are largely presynaptic, would correlate with changes in two other presynaptic markers: synaptophysin (Syn), a measure of synaptic density, and ChAT activity. The midfrontal (MF) cortex of 36 autopsy confirmed (NIA and CERAD criteria) AD patients (mean death age +/- SD 80.1 +/- 8.4 years) who met NINDS-ADRDA criteria for a clinical diagnosis of probable or possible AD, and 11 nondemented controls (mean death age +/- SD 77.9 +/- 8.0) were examined. Synapse counts were quantified by a dotimmunobinding assay for Syn. ChAT activity was assessed by standard biochemical assays. Nicotinic cholinergic receptor binding was assayed using the high affinity nicotinic agonist [3H]-(+/-)-epibatidine ([3H]-EPI). The mean +/- SD Syn in AD (83.4 +/- 31.9 arbitrary units (AU)/mg protein) was significantly lower than controls (126.1 +/- 19.9, p = 0.0003; t-test). The mean ChAT activity in AD (139.0 +/- 75.6 nmol ACh/hr/100 mg protein) was significantly lower than controls (219.6 +/- 70.8, p = 0.004). The mean [3H]-EPI total binding in AD (6.2 +/- 2.8 fmol/mg protein) was significantly lower than controls (14.8 +/- 3.2; p < 0.0001). Syn correlated with [3H]-EPI binding in AD (r = 0.48, p = 0.006; Pearson) but ChAT did not (r = -0.20, p = 0.34). We conclude that loss of high affinity nAChR binding correlates with loss of synapses in AD. The lack of correlation between [3H]-EPI binding and ChAT activity suggests that the targeted receptor populations may not be located exclusively on cholinergic neurons.     

Survival of Lubinus straight (IP) and curved (SP) total hip prostheses in 543 patients after 4-13 years

The clinical outcome and survival of 543 total hip arthroplasties with Lubinus cemented total hip prostheses after a mean of 7.9 years are reported. Clinical evaluation revealed no significant differences between patients with a straight stem and those with a curved anatomic stem. Loosening was statistically associated with young age, male sex, heavy weight, diagnosis other than osteoarthritis and year of operation. Survivorship analysis of the Lubinus IP implant at 8 years revealed a 95% chance of survival. The survival of the SP implant was 96%. After this time point the curve for SP implants began to fall at a faster rate than that for IP implants.