Ca(2+)-induced Ca2+ release mediates Ca2+ transients evoked by single action potentials in rabbit vagal afferent neurones

1. Standard intracellular recording techniques with 'sharp' micropipettes were used to evoke action potentials (APs) in acutely dissociated adult nodose neurones. 2. APs induced a transient increase in [Ca2+]i (a calcium transient), recorded with fura-2, that was dependent upon [Ca2+]o and the number of APs. Over the range of one to sixty-five APs, the relation between the amplitude of the calcium transient and the number of APs was well fitted by a rectangular hyperbola (chi 2 = 3.53, r = 0.968). From one to four APs, the calcium transient-AP relation can be described by a line with a slope of 9.6 nM AP-1 (r = 0.999). 3. Charge movement corresponding to Ca2+ influx evoked by a single AP was 39 +/- 2.8 pC (mean +/- S.E.M.) and did not change significantly during trains of one to thirty-one APs (P < 0.05). 4. Caffeine (10 mM), a known agonist of the ryanodine receptor, produced an increase in [Ca2+]i. The caffeine-induced rise in [Ca2+]i was attenuated (by > 90%) by lowering [Ca2+]o, and by ryanodine (10 microM), 2,5-di(t-butyl)hydroquinone (DBHQ, 10 microM), or thapsigargin (100 nM). 5. Neurones incubated with ryanodine, DBHQ or thapsigargin required at least eight APs to evoke a detectable calcium transient. These reagents did not significantly affect Ca2+ influx (P < 0.05). In the presence of these inhibitors, the calcium transient-AP relation exhibited slopes of 1.2, 1.1 and 1.9 nM AP-1 for ryanodine, DBHQ and thapsigargin, respectively. When compared with the slope of 9.6 nM AP-1 in non-treated neurones, it appears that Ca2+ influx produced by a single AP is amplified by ca 5- to 10-fold.

A nonradioisotope approach to study the in vivo metabolism of phosphorothioate oligonucleotides

A 25-mer phosphorothioate oligodeoxynucleotide (GEM 91) complementary to the gag gene mRNA of HIV-1 virus was administered intravenously (i.v.) at a dose of 10 mg/kg/day for 8 weeks or 25 mg/kg single dose subcutaneously (SC) to adult Rhesus monkeys. No radioactive markers were used. A capillary gel electrophoresis (CGE) method with UV detection was used to determine the concentration of GEM 91 in plasma and the metabolite profile. The metabolite profile was virtually the same following a single dose of either 10 mg/kg i.v. or 25 mg/kg SC. A different metabolite profile was observed after 4 or 8 weeks of multiple i.v. doses of 10 mg/kg/day. The extract was subjected to matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS) for positive identification. Mass spectrometry confirmed the major metabolic pathway in vivo to be via 3'-end exonuclease activity. The extract was then subjected to a hybridization-assisted ligation reaction in which only 5'-end intact metabolites were labeled. Analysis by CGE with laser-induced fluorescence (LIF) detection allowed each of these metabolites to be quantified with a limit of detection of 1 ppb (ng/ml). MALDI-TOFMS identified components digested from both ends of the DNA. This study demonstrates that the combination of quantitative CGE-LIF and MALDI-TOFMS yields a powerful and unique approach to study the metabolism of phosphorothioate oligonucleotides.

Improvement in the polyneuropathy associated with familial amyloid polyneuropathy after liver transplantation

OBJECTIVE

To study, following liver transplantation, the neurologic progression or regression of the polyneuropathy in a cohort of patients with familial amyloidotic polyneuropathy (FAP).

BACKGROUND

FAP is characterized by the relentless progression of neurologic and cardiac impairment, leading to death within 7 to 15 years after disease onset. No effective treatment to slow or halt the progression of this disease has been found to date.

DESIGN/METHODS

Over the past 3 years, our FAP patients were offered liver transplantation as treatment. We report on nine patients who were followed longitudinally with serial neurologic examinations since transplantation.

RESULTS

Clinically, all patients evaluated for neurologic progression reported significant improvement in general well being. No patient showed any progression in neurologic disease since receiving a liver transplant. Improvements are documented in symptomatic, autonomic, and sensorimotor neurologic disease in all patients.

CONCLUSION

Our experience suggests that liver transplantation may offer hope for arrest of progression and neurologic improvement in patients with FAP.

Facilitation of long-term potentiation by prior activation of metabotropic glutamate receptors

1. The influence of prior metabotropic glutamate receptor (mGluR) activation on subsequent long-term potentiation (LTP) induction was investigated with the use of the mGluR agonist 1-amino-cyclopentane-1S,3R-dicarboxylic acid (ACPD, 20 microM). Field potential recordings were made in the stratum radiatum of CA1 slices taken from young adult male rats and from which CA3 was routinely dissected. Theta burst stimulation (TBS) just above threshold was used to induce LTP. 2. A 10-min bath application of ACPD begun 30 min before the TBS facilitated the induction of LTP in a dose-dependent manner and resulted in an enhanced magnitude and stability of LTP. 3. ACPD did not enhance the degree of LTP induced by strong TBS, suggesting that it acts to lower the threshold for LTP induction but does not raise the ceiling on the amount of inducible LTP. 4. This priming effect by ACPD was stereo specific and lasted between 1 and 3 h. Synaptic stimulation during the ACPD application was not necessary for the enhancement of LTP. Blockade of N-methyl-D-aspartate receptors (NMDARs) during ACPD application also failed to affect the enhancement of LTP. 5. ACPD-induced priming of LTP was antagonized by L-2-amino-3-phosphonopropionic acid, suggesting an involvement of group I mGluRs. 6. ACPD-induced enhancement of LTP was not secondary to long-lasting changes in NMDAR activation or GABAAergic inhibition, because it was unaffected by the addition of picrotoxin, a gamma-aminobutyric acid-A (GABAA) receptor antagonist, and isolated NMDAR-mediated responses did not show a long-lasting enhancement in response to ACPD application. 7. These data demonstrate that activation of mGluRs can initiate persistent yet covert changes in synaptic function that facilitate the stable induction of LTP.

Repeatability of clinical measurements of the amplitude of accommodation

In order to determine whether a significant change has occurred in a clinical parameter, it is essential to assess the repeatability of the measurement procedure. Accordingly, the present study has examined the repeatability of three techniques for evaluating the subjective amplitude of accommodation. Clinical amplitudes were determined using the push-up, push-down and minus lens procedures in 13 young individuals (mean age: 24.3 years) on five separate occasions. The standard deviation (SD) of the five examinations was calculated for each individual and the mean values for the population sample determined. The mean SDs for the push-up, push-down and minus lens techniques were equivalent, with 95% confidence limits of approximately 1.4 D being observed for all three procedures. Furthermore, the mean amplitude recorded using the push-up technique was significantly higher than that observed for the other two procedures. It is concluded that a change of at least +/- 1.50 D should be adopted as the minimum significant shift in amplitude of accommodation for this group.

Pulmonary artery reconstruction for tuberculosis

A 35-year-old woman underwent reconstruction of her right pulmonary artery for treatment of acquired right pulmonary artery stenosis. The stenosis was secondary to tuberculosis causing both an extrinsic and an intrinsic obstructive component. After her reconstruction, the patient made an uneventful recovery, and perfusion to the right lung was subsequently restored.

Treatment of 100 patients with primary amyloidosis: a randomized trial of melphalan, prednisone, and colchicine versus colchicine only

PURPOSE

A clinical trial designed to test whether treatment with melphalan, prednisone, and colchicine (MPC) is superior to colchicine (C) alone was performed in patients with primary amyloidosis (AL), a nonmalignant plasma cell dyscrasia.

PATIENTS AND METHODS

Patients were randomized to MPC or C with stratification according to sex, time from diagnosis to study entry (ie, less than 3 months or 3 to 12 months), and dominant organ system involvement (ie, cardiac, renal, neurologic, or others). Data were gathered monthly from patients, quarterly from physicians, and annually in the Clinical Research Center. One hundred consecutive patients with AL amyloidosis admitted between 1987 and 1992 who met eligibility requirements were treated and followed for a minimum of 18 months. Fifty patients (group A) received daily oral colchicine and 50 patients (group B) received cycles of oral melphalan and prednisone every 6 weeks for 1 year as well as colchicine.

RESULTS

The principal outcome measure was median survival, which was compared in the two treatment groups and in the subgroups. The overall survival of all patients from study entry was 8.4 months. Comparing group A (C) to group B (MPC), the survival was 6.7 months versus 12.2 months (P = 0.087). Both treatment groups had poor survival for patients in the cardiac subgroup, longest survival in the renal group, and significant differences favoring MPC treatment only in patients whose major system manifestations were neurologic (P = 0.037) or other (P = 0.007). Multivariate analysis showed a strongly significant treatment effect (P = 0.003) and improved survival associated with not having cardiac or gastrointestinal involvement.

CONCLUSIONS

MPC was advantageous for patients whose major manifestations of amyloid disease were other than cardiac or renal. Better survival regardless of treatment was noted in patients for whom a satisfactory supportive treatment such as transplant or dialysis exists for their organ failure.

Conjugates of minor groove DNA binders with oligodeoxynucleotides: synthesis and properties

Oligodeoxynucleotide conjugates of netropsin (Nt) and distamycin A (Dst) were synthesized, and the thermal stability of several model DNA duplexes containing conjugates was studied. Two Dst residues conjugated at both ends of the oligonucleotide were needed for substantial increase in the melting temperature of the corresponding duplex (delta Tm > 30 degrees C). Two attached Dst residues had a greater effect on the Tm value than did two free molecules of Dst per duplex. In contrast to Dst, one Nt molecule linked to the oligonucleotide was enough to influence the thermal stability of the duplexes. Like Dst, the attached Nt appeared to stabilize duplexes much more than free Nt molecules. Attachment of Nt to either the 5'- or 3'-end of the different nonadeoxynucleotides containing 5' ...TTAAA... or 5' ...TATA... sites increased Tm of their duplexes by 21 degrees C-25 degrees C, whereas delta Tm for free Nt was 8 degrees C-15 degrees C (delta delta Tm = 10 degrees C-14 degrees C). The same phenomenon was shown for oligonucleotide phosphorothioates (delta Tm were 18 degrees C-22 degrees C and 9 degrees C-13 degrees C for attached and free Nt, respectively; delta delta Tm = 9 degrees C). This effect was even more pronounced for a hairpin oligonucleotide (delta delta Tm = 18 degrees C).

Sequencing of antisense DNA analogues by capillary gel electrophoresis with laser-induced fluorescence detection

A method using capillary gel electrophoresis with laser-induced fluorescence detection is described which permits complete sequence determination of antisense DNA analogues of unknown sequence. This method, originally created as a tool to confirm the sequence of antisense oligonucleotides being developed as therapeutic drugs, utilizes data collected under a range of experimental conditions described by the Ogston model as applied to gel electrophoresis. A linear relationship independent of experimental conditions between the relative electrophoretic migration time and the oligonucleotide base number was observed and is shown to be consistent with a simplified version of this model and can be used to facilitate the sequence determination.

Transplanting teeth successfully: autografts and allografts that work

This article suggests tooth transplantation as an alternative to other restorative options. The 10-year success rates for autografts--teeth moved from one location to another in a patient's mouth--range from 60 percent to 95 percent. Allografts, teeth moved from one person to another, are less successful. The authors report on one case of each type of transplant.

Quantitative analysis of phosphorothioate oligonucleotides in biological fluids using direct injection fast anion-exchange chromatography and capillary gel electrophoresis

The analysis of antisense phosphorothioate DNA (SODN) in human plasma via direct injection using anion-exchange high-performance liquid chromatography (AE-HPLC) is presented. The method relies on the ability to selectively extract phosphorothioate DNA from undigested serum, plasma and urine on anion-exchange resins. The automated HPLC method can analyze a sample every 5 min with a limit of detection of 50 ng/ml (ppb). The DNA was collected, desalted and analyzed by capillary gel electrophoresis. Due to the high resolving power of this technique, a qualitative assessment of enzymatic degradation of the antisense oligonucleotide can be made.

Combined treatment with terbutaline and aminophylline inhibits experimental amyloidosis in mice

OBJECTIVE

To investigate the effects of drugs known to elevate adenosine 3':5'-cyclic monophosphate (cAMP) on experimental amyloidosis.

METHODS

A beta 2-agonist, terbutaline, and a phosphodiesterase inhibitor, aminophylline, were administered in combination in a mouse model of amyloidosis induced by inflammatory stimulation with silver nitrate. Amyloidosis was quantitated by radioimmunoassay for splenic amyloid A (AA) protein.

RESULTS

At the doses selected, aminophylline/terbutaline inhibited splenic amyloid deposition more potently than did colchicine, a known inhibitor of amyloidosis.

CONCLUSION

Drugs known to elevate cAMP inhibit experimental mouse AA amyloidosis.

The epidemiology of AL and AA amyloidosis

The limited available epidemiological information on AL amyloidosis suggests that there may be differences between population-based studies and case series data with respect to variables such as age and racial patterns. Much more work in this area is required before specific aetiologic hypotheses can be tested. Most available data to approximate the epidemiology of AA amyloidosis are derived from autopsies. Most patients with AA amyloidosis die from causes other than amyloidosis, therefore mortality data based on death certificates is of limited value in AA amyloidosis. Case ascertainment in autopsy studies may be difficult due to the frequent lack of adequate histological controls. Establishment of registries for both AL and AA amyloidosis would facilitate epidemiological research in these disorders.

Nitric oxide regulates spike frequency accommodation in nodose neurons of the rabbit

A Ca(2+)-dependent slow spike after hyperpolarization (AHPslow) is present in about 35% of the neurons in the nodose ganglion. Although the AHPslow profoundly affects spike frequency accommodation of these neurons, the mechanisms that control the generation and the duration of the AHPslow are unclarified. N omega-Nitro-L-arginine methyl ester (L-NAME; 10 microM), a specific inhibitor of nitric oxide synthase (NOS), reduced the AHPslow by more than 92%. The L-NAME block of the AHPslow was antagonized by application of 50 microM S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide donor. The fast, Ca(2+)-dependent, spike after hyperpolarization preceding the AHPslow and the elevation of intracellular Ca2+ accompanying the AHPslow were unaffected by L-NAME treatment. These findings indicate that products of NOS activity might directly or indirectly activate the AHPslow K+ channels at a step beyond Ca2+ influx or intracellular Ca2+ mobilization.

Orthotopic liver transplantation for familial amyloidotic polyneuropathy

Orthotopic liver transplantation for inborn errors of metabolism has become a standard indication for transplantation in pediatric and adult patients with alpha-1 antitrypsin deficiency, Wilson's disease and tyrosinemia, amongst several less common diseases. Familial amyloidotic polyneuropathy (FAP) is a rare autosomal dominant disease whose metabolic origin lies in an abnormal protein synthesized primarily in the liver. FAP, also discussed as the autosomal dominant form of amyloidosis, is characterized as a hereditary form of amyloidosis. It is the rarest form of amyloidosis affecting kindreds of specific ethnic backgrounds. The true incidence of this disease in the United States is not known. The mutant protein, called transthyretin or prealbumin, forms amyloid fibrils which accumulate in vital tissues ultimately leading to the patient's death. Liver transplantation for this inherited disease leads to the production of normal transthyretin protein. This theoretically should arrest the disease process. The first 5 patients in the United States with FAP who have undergone transplantation are presented.

Proteins of the systemic amyloidoses

Significant advances were made this year in the understanding of serum amyloid A isotypes and in the definition of different amyloid light-chain proteins. Increasing numbers of hereditary amyloid-related transthyretin mutations have been reported (more than 30 to date). Two new hereditary amyloid proteins in several different kinships have appeared, ie, fibrinogen A alpha and lysozyme, each with a single point mutation. Both were found in patients with non-neurogenic hereditary amyloidosis with severe nephropathy. In islet amyloid polypeptide, the amyloid of adult-onset diabetes, the amino-acid sequence Ala-Ile-Leu-Ser at positions 25 to 28 appears to be critical for fibrillogenesis.

Clinical aspects of amyloidosis, including related proteins and central nervous system amyloid

In the beta/A4 protein of Alzheimer's disease, on chromosome 21, three mutations at the same locus have been described (Val 717 Ile, Val 171 Phe, and Val 171 Gly). The heterogeneity of the disease was indicated in individuals with mutations involving chromosomes 19 and 14 as well. beta Protein has also been demonstrated in the rimmed vacuoles of inclusion-body myositis. Therapeutic advances include orthotopic liver transplantation to remove the site of synthesis of the mutant transthyretin molecule. Clinical manifestations of the various forms of amyloidosis involve virtually every system in the body; the breadth of the curious series of proteins called amyloid has been extended considerably in the past year.

DNA sequencing by capillary electrophoresis: use of a two-laser-two-window intensified diode array detection system

This paper presents the principles of an instrument designed for DNA sequencing using the standard four-dye-labeled primer approach. The method is based on capillary electrophoresis with laser-induced fluorescence and an intensified diode array detector. An important goal of the instrument design has been a detection system that possesses high sensitivity and high spectral resolution. Based on an analysis of the spectral characteristics of the four standard dye-labeled primers, FAM, JOE, ROX, and TAMRA, the strategy has been to use a two-laser-two-window approach, in which a 488-nm argon ion laser illuminates one window, followed by a 543-nm helium-neon laser illuminating the second window. The two-window approach has no moving parts and permits continuous illumination. Spectral resolution is provided by a grating spectrograph and a cooled intensified diode array. The estimated limit of detection for the standard four dye-labeled primers was found to be in the sample concentration range of 1 x 10(-12) M. To achieve these low levels, complete free-radical polymerization of polyacrylamide has been found to be necessary in order to reduce background noise. In addition, reduction in background noise was accomplished by continual purging of the anodic reservoir in order to prevent electrolysis products from entering the capillary. Separation of DNA sequencing reaction products is demonstrated on a 9% T linear polyacrylamide column.