Sensitive trace-first liquid chromatographic determination of 4-aminopyridine in 3,4-diaminopyridine

For the treatment of human neuromuscular diseases, 3,4-diaminopyridine (DAP) is six to ten times more effective than 4-aminopyridine (AP), but only half as convulsant and toxic. Therefore, there is a need for the determination of AP in DAP. With only conventional equipment, high-pressure liquid chromatography can be used for the extremely sensitive detection of a trace contaminant under one condition: that is, the trace must be eluted before the major component it contaminates. Prior elution presents a trace peak in a fully exploitable form that is maximally efficient and maximally observable. This has already been demonstrated with a Pirkle-concept chiral stationary phase for determination of a chiral trace. However, its application to determination of a nonchiral trace with a reversed phase has not previously been reported. Such an application is reported here. In this demonstrative study, selectivity and loading capability were iteratively improved. Ion pairing with dodecanesulfonate maximized selectivity. It was again shown that using a less concentrated sample in greater volume maximizes loading capability without obscuring the peak of the trace. Eventually, the ability to detect 0.005% AP in DAP was demonstrated. Whether that sensitivity might be improved still more, perhaps with a larger column, was not established.     

Glued-on, rigid gas-permeable contact lens for severe radiation-induced keratitis.

A 68-year-old woman with severe radiation-induced keratoconjunctivitis sicca became progressively unresponsive to conventional medical treatment. Her left eye deteriorated rapidly and required total tarsorrhaphy. In an attempt to stabilize the right eye and preserve some functional vision, we glued a high-Dk rigid, gas-permeable contact lens with tissue-grade cyanoacrylate adhesive to Bowman's membrane. This glued-on contact lens induced rapid and dramatic improvement of the patient's comfort and sight. Recent developments in high-permeability, rigid, contact-lens materials now make artificial replacement of the epithelium a potentially useful treatment for severe ocular surface disease when conventional treatment has failed.     

Gangliosides and sialoglycoproteins in hypothalamus of normal, postnatal, and pre- and postnatal protein undernourished rats.

Total ganglioside and sialoglycoprotein concentrations were determined in the hypothalamus of normal (diet: 25% casein), postnatal undernourished (diet: 8% casein since birth), and pre- and postnatal undernourished rats (diet: 8% casein since pregnancy). Hypothalamic weights for the two low protein diet groups were lower than for the normal diet groups at all ages studied. Total hypothalamic ganglioside and sialoglycoproteins (mumol NANA) of postnatal undernourished rats were lower than control at day 10, while in pre- and postnatal undernourished rats this difference occurred at day 7. The reduction in gangliosides and sialoglycoprotein contents was not solely a consequence of the decrease in hypothalamic weight since, when the data were expressed as nmol NANA/mg tissue, similar reductions were observed principally in the pre- and postnatal protein undernutrition group. These results suggest that the effects of pre- and postnatal undernutrition on hypothalamic gangliosides and sialoglycoproteins are more pronounced than those that occur as a result of postnatal undernutrition.     

Leukaemia Inhibitory Factor or Related Factors Promote the Differentiation of Neuronal and Astrocytic Precursors within the Developing Murine Spinal Cord

Previously we have shown that leukaemia inhibitory factor (LIF) potentiates the development of murine spinal cord neurons in vitro , suggesting that it, or related factors, may play an important regulatory role in neuronal development. We have further investigated this role and show here that the generation of neurons in cultures of embryonic day 10 spinal cord cells is inhibited by antibodies to the β subunit of the LIF receptor. Since there are more undifferentiated precursors in antibody-treated cultures than in control and LIF-treated cultures, it is concluded that the primary action of LIF, or related molecules, is to promote neuronal differentiation, not precursor survival. In addition, the failure of LIF to support neuronal survival in the period immediately following differentiation suggests that the increased numbers of neurons generated with LIF are not attributable to its neurotrophic action. By selecting neuronal precursors on the basis of their inability to express class I major histocompatibility complex molecules, it was shown that LIF acted directly upon these cells and not via an intermediary cell. LIF also appears to be involved in regulating the differentiation of astrocytes, since it increases the number of glial fibrillary protein (GFAP)-positive cells present in the cultures and since the spontaneous production of GFAP-positive cells is blocked by antibodies to the LIF β receptor. These findings suggest that LIF or related factors promote the differentiation of neural precursors in the spinal cord, but that they are not involved in preferentially promoting precursors down a specific differentiation pathway.     

Intravenous 6-thioguanine or cisplatin, fluorouracil and leucovorin for advanced non-small cell lung cancer: a randomized phase II study of the cancer and leukemia group B.

This randomized phase II study was designed to evaluate the activity of intravenous 6-thioguanine (6-TG) as a single agent and the combination of cisplatin and 5-fluorouracil (5-Fu) modulated by oral leucovorin (PFL) in patients with advanced non-small cell lung cancer (NSCLC). Eligible patients had measurable or evaluable stage III B or IV NSCLC, had no received prior chemotherapy and had a performance status of 0-2. Patients were randomized to treatment with intravenous 6-TG at 55 mg/m2 administered over 30 minutes for 5 consecutive days and repeated every 35 days, or PFL chemotherapy with cisplatin 100 mg/m2 on day 1, 5-FU 800 mg/m2/day as a continuous intravenous infusion over 5 days and oral leucovorin administered at 100 mg every 4 hours during the entire duration of the cisplatin and 5-FU infusions. PFL was repeated every three weeks. Ninety-five eligible patients were randomized, 46 to 6-TG and 49 to PFL. Response rates were 4% for 6-TG (95% confidence interval 0.5%-14.8%, 1 partial, and 1 complete response) and 29% (16.6%-43.3%) for PFL (all partial). The median time to treatment failure was 2 and 4 months, respectively, and the median survival times were 6 and 10 months, respectively. Toxicities with 6-TG were, generally, mild to moderate but severe or life-threatening granulocytopenia was observed in 21% of patients. With PFL, mucositis was dose-limiting, and 78% of patients had severe or life-threatening mucositis. This led to dose reduction of 5-FU and leucovorin during subsequent cycles or treatment termination in 82% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dendritic competition: competition for what?

A lesion to the retina of a newborn rat results in the retrograde degeneration of ganglion cells in a sector of retina peripheral to the lesion. The dendritic tree of ganglion cells bordering the region depleted of ganglion cells have their dendrites preferentially directed into this area. We have examined the factors which play a role in this rearrangement of the dendritic tree. The results show that the lesion in neonates selects for or produces a population of cells with the axon directed away from the depleted area and primary dendrites directed towards the depleted area. The abnormal dendritic bias cannot be accounted for solely on the basis of a decrease in contact inhibition since a reduction in the density of all ganglion cells by 30% prior to making the retinal lesion does not attenuate the abnormal dendritic bias into the depleted area. The abnormal dendritic bias is present in animals operated on up to 15 days of age postnatally but not in more mature animals. The abnormal dendritic bias develops prior to the formation of a large number of synapses in the inner nuclear layer. Our results cannot be easily accounted for by competition for synaptic contacts or a loss of contact inhibition as previously suggested. We propose that chemotropic factors produced within the area depleted of ganglion cells induce the abnormal dendritic bias and the number of synaptic contacts may limit the size of the dendritic field.     

Trypsin interaction with the senile plaques of Alzheimer disease is mediated by β-protein precursor

In this study we demonstrate byin situ binding that trypsin interacts with the senile plaques found in Alzheimer disease. Characterization of various potential trypsin binding proteins shows that trypsin binding is mediated by β-protein precursor (βPP)—the progenitor of amyloid-β in senile plaques. Using specific antisera against various proteins to sterically block trypsin blocking, we found that only those antibodies raised against proteins or peptides containing the Kunitz protease inhibitor domain were able to abolish binding. By analogy with other protease/inhibitor interactions, we speculate that the binding of trypsin to βPP could involve concomitant βPP cleavage. Therefore, βPP in protecting against potentially damaging proteolysis could simultaneously liberate βPP fragments or intermediate precursors of amyloid-β deposits.