Poly(1-vinyl-2-pyrrolidinone) hydrogels as vitreous substitutes: histopathological evaluation in the animal eye

A homopolymer of 1-vinyl-2 pyrrolidinone and its copolymer with 2-hydroxyethyl methacrylate, both cross-linked with divinyl glycol, were produced as possible substitutes for the vitreous body of the eye. The hydrated polymers behaved like viscoelastic gels, displaying excellent physical and optical properties. The sterile gels (0.7-1.5 ml) were injected into the vitreous cavity of rabbits, which previously underwent gas-mediated vitrectomy. Clinically, the eyes were quiet, with the exception of transient opacities in the vitreous. After 4 weeks, the operated eyes were enucleated and subjected to histopathological analysis using light and transmission electron microscopy. The common feature in all sections was the invasion of inflammatory cells. Vacuoles containing granular material, assumed to be polymer, were seen in the intercellular spaces of the neural retina, in the retinal pigment epithelium cells, and in macrophages. These findings indicated the fragmentation and phagocytosis of synthetic gels. It appeared that the biodegradation of the internalized polymers did not proceed further, however, the fate of polymers and their usefulness as vitreous substitutes should be investigated through long-term experiments.     

Directional organization of eye movement and visual signals in the floccular lobe of the monkey cerebellum

The floccular lobe of the monkey is critical for the generation of visually-guided smooth eye movements. The present experiments reveal physiological correlates of the directional organization in the primate floccular lobe by examining the selectivity for direction of eye motion and visual stimulation in the firing of individual Purkinje cells (PCs) and mossy fibers. During tracking of sinusoidal target motion along different axes in the frontoparallel plane, PCs fell into two classes based on the axis that caused the largest modulation of simple-spike firing rate. For "horizontal" PCs, the response was maximal during horizontal eye movements, with increases in firing rate during pursuit toward the side of recording (ipsiversive). For "vertical" PCs, the response was maximal during eye movement along an axis just off pure vertical, with increases in firing rate during pursuit directed downward and slightly contraversive. During pursuit of target motion at constant velocity, PCs again fell into horizontal and vertical classes that matched the results from sinusoidal tracking. In addition, the directional tuning of the sustained "eye velocity" and transient "visual" components of the neural responses obtained during constant velocity tracking were very similar. PCs displayed very broad tuning approximating a cosine tuning curve; the mean half-maximum bandwidth of their tuning curves was 170-180 degrees. Other cerebellar elements, related purely to eye movement and presumed to be mossy fibers, exhibited tuning approximately 40 degrees narrower than PCs and had best directions that clustered around the four cardinal directions. Our data indicate that the motion signals encoded by PCs in the monkey floccular lobe are segregated into channels that are consistent with a coordinate system defined by the vestibular apparatus and eye muscles. The differences between the tuning properties exhibited by PCs compared with mossy fibers indicate that a spatial transformation occurs within the floccular lobe.     

Substituted glycals as probes of glycosidase mechanisms

D-Glucal and a series of substituted derivatives have been tested as substrates, inhibitors and inactivators of the Agrobacterium faecalis beta-glucosidase in order to probe structure/function relationships in this enzyme. D-Glucal is shown to be a substrate (kcat = 2.3 min-1, Km = 0.85 mM) undergoing hydration with stereospecific protonation from the alpha-face to yield 2-deoxy-beta-D-glucose. 1-Methyl-D-glucal surprisingly serves as only a poor substrate (kcat = 0.056 min-1, Km = 57 mM), also undergoing protonation from the alpha-face. 2-Fluoro-D-glucal, however is completely inert, as a result of inductive destabilisation of the oxocarbenium ion-like transition state for protonation, and functions only as a relatively weak (Ki = 24 mM) inhibitor. Similar behaviour was seen with almond beta-glucosidase and yeast alpha-glucosidase and for the interaction of 2-fluoro-D-galactal with Escherichia coli beta-galactosidase. A series of of alpha, beta-unsaturated glucal derivatives was also synthesised and tested as potential substrates, inhibitors or inactivators of A. faecalis beta-glucosidase. Of these only 1-nitro-D-glucal functioned as a time dependent, irreversible inactivator (ki = 0.011 min-1, Ki = 5.5 mM), presumably acting as a Michael acceptor. Electrospray mass spectrometric analysis revealed multiple labeling of the enzyme by this inactivator, lessening its usefulness as an affinity label. Less reactive Michael acceptor glycals which might have been more specific (1-cyano-, 2-cyano-, 1-carboxylic acid, 1-carboxylic acid methyl ester) unfortunately did not function as inactivators or substrates, only as relatively weak reversible inhibitors (Ki = 3-96 mM).     

Repressor titration: a novel system for selection and stable maintenance of recombinant plasmids

The propagation of recombinant plasmids in bacterial hosts, particularly in Escherichia coli, is essential for the amplification and manipulation of cloned DNA and the production of recombinant proteins. The isolation of bacterial transformants and subsequent stable plasmid maintenance have traditionally been accomplished using plasmid-borne selectable marker genes. Here we describe a novel system that employs plasmid-mediated repressor titration to activate a chromosomal selectable marker, removing the requirement for a plasmid-borne marker gene. A modified E.coli host strain containing a conditionally essential chromosomal gene (kan) under the control of the lac operator/promoter, lac O/P, has been constructed. In the absence of an inducer (allolactose or IPTG) this strain, DH1 lackan , cannot grow on kanamycin-containing media due to the repression of kan expression by LacI protein binding to lac O/P. Transformation with a high copy-number plasmid containing the lac operator, lac O, effectively induces kan expression by titrating LacI from the operator. This strain thus allows the selection of plasmids without antibiotic resistance genes (they need only contain lac O and an origin of replication) which have clear advantages for use as gene therapy vectors. Regulation in the same way of an essential, endogenous bacterial gene will allow the production of recombinant therapeutics devoid of residual antibiotic contamination.     

Androgen-dependent protein interactions within an intron 1 regulatory region of the 20-kDa protein gene

The 20-kDa protein gene is androgen regulated in rat ventral prostate. Intron 1 contains a 130-base pair complex response element (D2) that binds androgen (AR) and glucocorticoid receptor (GR) but transactivates only with AR in transient cotransfection assays in CV1 cells using the reporter vector D2-tkCAT. To better understand the function of this androgen-responsive unit, nuclear protein interactions with D2 were analyzed by DNase I footprinting in ventral prostate nuclei of intact or castrated rats and in vitro with ventral prostate nuclear protein extracts from intact, castrated, and testosterone-treated castrated rats. Multiple androgen-dependent protected regions and hypersensitive sites were identified in the D2 region with both methods. Mobility shift assays with 32P-labeled oligonucleotides spanning D2 revealed specific interactions with ventral prostate nuclear proteins. Four of the D2-protein complexes decreased in intensity within 24 h of castration. UV cross-linking of the androgen-dependent DNA binding proteins identified protein complexes of approximately 140 and 55 kDa. The results demonstrate androgen-dependent nuclear protein-DNA interactions within the complex androgen response element D2.     

Structural characterization of the molecular dimer of the peptide antibiotic vancomycin by distance geometry in four spatial dimensions

OBJECTIVE: The objectives of this study were to know the prevalence of hepatitis C virus (HCV) in a population of pregnant women, to evaluate the vertical transmission rates of HCV in a prospective study and to determine the repercussions and consequences in children born to infected mothers. PATIENTS AND METHODS: A total of 6556 pregnant women were tested for HCV antibodies from January 1993 to August 1995. We followed 50 babies born to infected mothers for at least 12 months (mean 15 months). Serological assays employed included a screening ELISA II confirmed with immunoblot. Viral detection was performed by qualitative and quantitative PCR for HCV-RNA. RESULTS: Fifty-nine pregnant women were AcHCV(+). This represents a seroprevalence of 0.9%. Of the 50 babies followed, 6 were PCR(+) and 44 were PCR(-). The risk of transmission is correlated with the titer of HCV-RNA in the mother. All mothers of infected babies were HIV (-). CONCLUSIONS: The rate of prevalence in our pregnant women population is 0.9%. We found a vertical transmission rate of 12%. The high serum HCV-RNA titers in the mothers are a risk factor of transmission of HCV. The viremia in the children does not predict the apparition of the clinical disease, although they can exhibit intermittent increases of transaminases.     

Phase II trial of 9-aminocamptothecin administered as a 72-hour continuous infusion in metastatic colorectal carcinoma

PURPOSE: The camptothecin derivative irinotecan has demonstrated clinical activity in metastatic colorectal carcinoma in both chemotherapy-naive and fluorouracil-refractory patients. 9-Aminocamptothecin (9-AC; NSC 603071), another camptothecin derivative, was selected for clinical development based on preclinical activity, including cures in human tumor xenografts resistant to standard anticancer agents. We report a phase II trial of 9-AC in patients with previously untreated metastatic colorectal carcinoma. PATIENTS AND METHODS: Colorectal cancer patients with measurable disease, a performance status of 0 to 2 (Zubrod), and no prior chemotherapy for metastatic disease received 9-AC. A cycle of therapy was 35 microg/m2/h for 72 consecutive hours (840 microg/m2/d for 3 days) and rest on days 4 to 14; a course of therapy was defined as two cycles (28 days). Patients were assessed for response after two courses. RESULTS: Seventeen patients with metastatic colorectal cancer were entered onto this trial. No complete or partial responses were noted. Treatment was well tolerated; toxic effects consisted mainly of neutropenia, nausea, vomiting, stomatitis, fatigue, and anemia. Grade 3 to 4 toxicity was limited to neutropenia (grade 3 in four patients and grade 4 in six), anemia (grade 3 in two patients), and vomiting (grade 3 in two patients). No grade 3 or 4 diarrhea occurred. Only two patients had their 9-AC dose reduced to 30 microg/m2/h. The median nadir absolute granulocyte count (AGC) was 1,500/microL. The median number of courses given was two and the median time to disease progression was 8 weeks. CONCLUSION: At the dose and schedule used in this trial, 9-AC lacked antitumor activity in metastatic colorectal cancer. 9-AC infusion schedules of longer duration are currently being investigated in this disease.     

Healthy aging. A women''s issue

In this thesis, Korean prisoners' health behavior and the characteristics of their medical utilization were surveyed and analysed. Because prisoners are inclined to be mediators of communicable diseases or unhealthy behaviors between prison institution and the outside world, health care for prisoners is directly related to the national population. Data were collected through a self-administered survey of 5 Korean prisons out of a total of 38 correctional facilities and analysed in accordance with a causal model based on a path frame, by serial multiple regressions on health behavior, health status, and medical utilization, etc. According to the survey analysis, while prisoners were generally concerned with their health much more than they were before imprisonment, they perceived that their health status had deteriorated after imprisonment, and that their need for health services was increasing gradually during their time in prison. In the path analysis on the causal relations among variables related to the prisoners' health status and medical utilization, the prisoners' characteristics affected their health concern and health behavior, and subsequently affected their health status and medical utilization, respectively. To sum up these exploratory studies on prisoners' health behavior and health service utilization, some efforts to organize a health care system embracing the correctional institution and health care administration should be made on the level of establishing a health care delivery system for special social groups like prisoners.