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.

Localized amyloidosis of the larynx: evidence for light chain composition

We report the biochemical characterization of amyloid fibrils from a patient with localized amyloidosis of the epiglottis and larynx. Biopsy specimens showed amorphous material consistent with amyloid deposits with a plasmacytic infiltrate. Both plasma cells and amyloid deposits stained positively by immunohistochemistry for kappa light chains. Amyloid fibrils were isolated. The major constituent resolved as a 13 kd band was sequenced and found to be consistent with a kappa 1 light chain. A tryptic digest was carried out and 3 tryptic peptides were sequenced defining the first 45 residues of the protein and residues 110 through 119. Four amino acid substitutions were found, 3 of which have not been described previously. This study defines the immunoglobulin origin of amyloid deposits in localized amyloidosis. The benign nature of localized amyloidosis suggests that a localized clone of plasma cells producing an amyloidogenic light chain may represent the pathogenetic mechanism of this disease, which appears to be a form of plasma cell dyscrasia.

Separation of DNA fragments by capillary electrophoresis using replaceable linear polyacrylamide matrices

The use of low percent (1.5-6% T) replaceable linear polyacrylamide (LPA) network matrices for rapid separation of double-stranded DNA fragments was explored. Separations of fragments ranging from 20 to 23,000 base pairs were readily achieved. Typically, 4 x 10(6) theoretical plates/m were obtained in less than 30 min. Short separation times under 2 min were also possible, using the DNA intercalating dye, ethidium bromide, along with high electric fields. The high resolving power of linear polyacrylamide was demonstrated in the separation of two fragments which differ by a single base pair (123/124 base pairs) using 6% T LPA and ethidium bromide intercalation. This LPA composition allowed for the possible single base-pair resolution of dsDNA fragments up to 300 base pairs in length. Several concentrations of the linear polyacrylamide for different ranges of fragment lengths have been employed. In addition, replaceable LPA offers the advantage of a fresh separation matrix for each run, thus overcoming column stability problems and minimizing needs for sample cleanup. Electro-osmotic flow was substantially reduced using stable capillary coatings, which were required for obtaining high efficiencies and good reproducibility.

Quantitative analysis of phosphorothioate oligonucleotides in biological fluids using fast anion-exchange chromatography

Phosphorothioate oligonucleotides are potentially useful as anti-viral drugs. Classical DNA extraction methods are not as effective on short single-stranded DNA as with longer double-stranced chains. The classical method of phenol-chloroform extraction followed by ethanol precipitation is difficult to quantify, thus monitoring of the pharmacological disposition of these compounds is subject to error. A method has been devised and validated for extraction and analysis of modified oligonucleotides from biological fluids such as urine and serum based on protein kinase digestion and phenol-chloroform extraction. Due to the high native ultraviolet absorbance of the oligomers, detection limits in the low ppb range were obtained without derivatization.

Advances in amyloidosis

Major advances of the past year in the amyloidoses include a better understanding of the polymorphism of the acute-phase reactant serum amyloid A protein and the appearance of a new mouse model for primary amyloidosis. The list of single point mutations in transthyretin in different families with slightly varied clinical manifestations of the disease continues to grow. Gelsolin, with its asparagine 187 mutation, was found to cause amyloidosis beyond the borders of Finland, where it has been extensively evaluated. The incredible range of osteoarticular lesions due to beta 2-microglobulin in hemodialysis amyloidosis continues to expand and includes severe manifestations of spondyloarthropathy. The greatest number of papers in the amyloid literature have involved amyloid beta protein, amyloid beta protein precursor associated with Alzheimer's disease, and prion protein associated with the spongiform encephalopathies. The widespread systemic involvement of amyloidosis has led to the appearance of a host of manifestations, some common and some rare. Treatment advances focus on the use of liver transplantation in familial amyloid polyneuropathy to remove the source of mutant protein synthesis.

Intraperitoneal amyloid formation by amyloid enhancing factor — rich macrophages in ascitic fluid

Although resident peritoneal cells from amyloidotic mice (amyloidotic peritoneal cells) are capable of processing the precursor protein of secondary amyloidosis, serum amyloid A (SAA) to amyloid fibrils, the peritoneum is a rare site for amyloid deposition. This is considered to be due to a deficiency of SAA in the peritoneum. To increase the supply of SAA to the peritoneum, ascitic fluid containing about the same protein constituents as in the serum was induced in mice. Amyloidotic peritoneal cells were packed in a microchamber which was shielded with filter membranes, and cultured in ascitic fluid supplemented with additional inflammatory factors. On the 7th day, Congo red-positive structures which showed green birefringence under polarized light were found inside and occasionally outside the chamber. By anti-AA or -SAA immunostaining, amyloid deposits and the cell surfaces of macrophages were positive. Immunologic depletion of T- and B-lymphocytes from the amyloidotic peritoneal cells did not adversely effect the amyloid formation in microchambers. These results suggest that either ascitic fluid containing sufficient amounts of SAA, or peritoneal macrophages with a high amyloid enhancing factor (AEF) activity are indispensable for AA amyloid fibrillogenesis in the peritoneum.

High-performance capillary electrophoresis of SDS-protein complexes using UV-transparent polymer networks

This paper demonstrates the use of UV-transparent replaceable polymer networks for the separation of SDS-protein complexes on the basis of molecular weight. First, the use of linear (i.e. non-cross-linked) polyacrylamide is shown to provide molecular separation of SDS-protein complexes. A study reveals such columns to yield significantly greater lifetime than cross-linked gels because of the flexibility of the noncovalently attached polymer chains. However, column lifetime was still found to be limited (approximately 20-40 injections), and detection at 214 nm was problematical because of the absorbance of polyacrylamide. UV-transparent polymer networks of dextran and PEG were substituted for polyacrylamide with successful molecular weight sieving of SDS-protein complexes at 214 nm. Due to their low to moderate viscosities, these networks could be routinely replaced leading to the possibility of hundreds of injections with a single column. Migration time reproducibilities of 0.5% RSD or less were found with replacement of the network. Using dextran, calibration plots of peak area vs concentration of standard protein were linear over the range of 0.5 microgram/mL up to at least 0.25 mg/mL. Furthermore, plasma samples could be directly utilized because of the strong solvating power of SDS. Rapid separation of protein mixtures are demonstrated with these UV-transparent polymer networks.

Demonstration of plasma proteinase inhibitors in beta 2-microglobulin amyloid deposits

beta 2-microglobulin-related amyloidosis (A beta 2M) represents a frequent complication in long-term dialysis patients. Although the pathogenetic mechanism has yet to be fully understood, it is known that amyloid fibrils usually consist of intact molecules of beta 2-microglobulin (beta 2m). Plasma proteinase inhibitors (PPI) are a broad family of glycoproteins with the function of eliminating unwanted proteolysis of serine proteases. Their role in amyloidogenesis has become a subject of intense discussion, especially since the recent identification of alpha 1-antichymotrypsin in the beta-protein amyloid deposits of Alzheimer's disease. We evaluated immunohistochemically and biochemically the presence and distribution of several PPIs (alpha 1-proteinase inhibitor, alpha 1-antichymotrypsin, antithrombin III, alpha 2-macroglobulin and tissue inhibitor metalloproteinase) and amyloid P component in A beta 2M deposits in osteo-articular and visceral tissues from dialysis patients with amyloidosis, as well as two carpal tunnel synovia from non-dialysis patients and one Alzheimer's brain as controls. The immunohistochemical study demonstrated that all but one (anti-alpha 1-antichymotrypsin) of the PPI antibodies tested showed varying degrees of positive reaction against A beta 2M deposits. All the antibodies (including anti-alpha 1-antichymotrypsin) also reacted to some extent with other non-amyloid visceral and connective tissue elements diffusely and/or selectively. Among them, only the reaction of anti-amyloid P component had significantly distinctive localization to A beta 2M deposits, which were identified in adjacent serial sections by Congo red staining and immunohistochemical reaction against anti-beta 2m.(ABSTRACT TRUNCATED AT 250 WORDS)

A New Transthyretin Mutation Associated with Amyloidotic Vitreous Opacities

An inherited type of amyloidosis was suspected in an individual of Italian descent who presented with vitreous opacities. Although no family history of amyloidosis was apparent, the patient's transthyretin gene was examined and found not to possess any of the known transthyretin mutations. Complete DNA sequencing revealed a substitution of adenine for thymine in the second base of codon 84 causing an amino acid change of asparagine for isoleucine. The mutation was confirmed by demonstrating the loss of an Sfa N1 restriction endonuclease site. Allele-specific DNA amplification by polymerase chain reaction also was used to confirm the mutation. Either of these tests can be used for diagnosis. Asparagine 84 represents the second mutation associated with amyloidosis to occur at codon 84.

Amyloid and amyloidosis

Discovery of the different proteins that constitute the multiple types of amyloid has led to an increasing variety of studies in the literature of diverse medical subspecialties. In fact, in this review, the editors have chosen to review the beta 2-microglobulin amyloid of long-term hemodialysis in the section on renal disease. The current review focuses on the rapidly advancing basic studies of familial, amyloid A protein amyloid and the relevant clinical studies, although the research on amyloid light-chain protein and other forms of amyloidosis is also noted.

Familial amyloidotic polyneuropathy: a new transthyretin position 30 mutation (alanine for valine) in a family of German descent

Familial amyloidotic polyneuropathy (FAP) is a dominantly inherited form of amyloidosis usually associated with an abnormal transthyretin (TTR), previously known as prealbumin. Several disease-related variants of the protein, each with a different amino acid substitution and correlating DNA point mutation, have been identified. The TTR gene from a patient suffering from this disorder was asymmetrically amplified and directly sequenced, revealing a cytosine for thymine substitution in the second base of codon 30 and the creation of a novel Cfo I restriction endonuclease site in exon 2. This mutation results in a previously undescribed substitution of an alanine for valine in the final TTR protein. Analysis of the amino acid mutation reveals it to be a hydrophilic substitution at a hydrophobic core position. Alanine at position 30 represents the second FAP-associated mutation at position 30 in TTR.

Influence of column temperature on the electrophoretic behavior of myoglobin and alpha-lactalbumin in high-performance capillary electrophoresis

The influence of column temperature on the electrophoretic behavior of myoglobin and alpha-lactalbumin in high-performance capillary electrophoresis (HPCE) is presented. The major effect of temperature is to shorten the analysis time by decreasing the viscosity, but specific temperature effects on the protein migration behavior were also observed. Myoglobin, under high field (350 V/cm), was essentially temperature stable from 20 to 45 degrees C, but at constant current, a second form of myoglobin could be detected at both 214 and 410 nm. The initial form appeared to correspond to the Fe3+ and the second to the Fe2+ oxidation state of the heme iron. The rate of conversion from Fe3+ to the reduced Fe2+ in myoglobin, under given electrophoretic conditions, followed first-order kinetics with a rate constant at 30 degrees C of 304 s-1. A second protein, alpha-lactalbumin type III, demonstrated a conformational transition that resulted in asymmetric peaks and sigmodial mobility plots versus temperature in the transition region.

Analysis and use of the perforated patch technique for recording ionic currents in pancreatic beta-cells

We have used the nystatin perforated patch technique to study ionic currents in rat pancreatic beta-cells. The access resistance (Ra) between the pipette and the cell cytoplasm, measured by analyzing capacitive currents, decreased with a slow exponential time course (tau = 5.4 +/- 2.7 min) after seal formation. As Ra decreased, the magnitude of voltage-dependent K and Ca currents increased with a similar time course, and their activation kinetics became faster. After Ra stabilized, the macroscopic currents remained stable for up to an hour or more. When the final Ra was sufficiently low, Ca tail currents could be resolved which had properties similar to those recorded with the classical whole-cell technique. Two types of K channels could be characterized with perforated patch recordings of macroscopic K currents: (i) ATP-blockable K (KATP) channels which generate a time and voltage independent current that is blocked by glyburide and enhanced by pinacidil and (ii) voltage-dependent K (Kv) channels. Whole-cell recordings of KATP currents in the absence of ATP in the pipette showed that the maximum KATP conductance of the beta-cell was 83.8 +/- 40 nS. Perforated patch recordings show that the resting KATP conductance is 3.57 +/- 2.09 nS, which corresponds to about 4% of the channels being open in the intact beta-cell. In classical whole-cell recordings. Kv activation kinetics become faster during the first 10-15 min of recording, probably due to a dissipating Donnan potential. In perforated patch recordings where the Donnan potential is very small, Kv activation kinetics were nearly identical to the steady-state whole cell measurements.

Proline at position 36: a new transthyretin mutation associated with familial amyloidotic polyneuropathy

Familial amyloidotic polyneuropathy (FAP) is associated with the deposition of an abnormal transthyretin (TTR) molecule. We have studied DNA from a family of Greek descent with FAP. The proband's TTR gene was asymmetrically amplified by using PCR and then was sequenced directly, to reveal a cytosine-for-guanine substitution in codon 36. This substitution removes a recognition site for endonuclease Fnu4HI. Allele-specific PCR was employed for diagnosis of the mutation. The predicted amino acid change of alanine to proline at position 36 was confirmed by protein sequencing of the proband's plasma TTR.

Amyloidosis

Amyloidosis is a disease involving the fibrillar deposition of proteins in a manner that uniformly leads to the presence of green birefringence on polarization microscopy after staining the involved tissues with Congo red. In the year summarized, a wide range of new information has accumulated about this disease. In this article, attention has been paid to several newly described proteins now known to precipitate into amyloid deposits, including the proteins transthyretin, apolipoprotein A-1, cystatin C, gelsolin, amyloid beta protein, beta 2-microglobulin, scrapie protein, and islet amyloid polypeptide. The number of these amyloid-related proteins has resulted in the need for a revised nomenclature and classification scheme. The results of a recent international symposium addressing this issue are summarized in table form. The varied clinical manifestations of amyloidosis are described according to organ system, with unusual or unique areas of involvement noted. Finally, the treatment of amyloidosis and its prognosis are addressed, and new areas of possible intervention suggested.

A new transthyretin variant from a patient with familial amyloidotic polyneuropathy has asparagine substituted for histidine at position 90

A new transthyretin variant which lost an Sph I cleavage site within exon 3 has been characterized. A 260 bp sequence containing exon 3 was amplified using the polymerase chain reaction, and the variant was found to possess a Bsm I cleavage site not present in normal transthyretin. This led to the conclusion that the histidine at position 90 was replaced by asparagine, and amino acid analysis supported the conclusion. The discovery of this mutation suggests that intermolecular binding between hydrophobic polypeptide loops on the surface of transthyretin can lead to familial amyloidotic polyneuropathy.

Separation of DNA restriction fragments by high performance capillary electrophoresis with low and zero crosslinked polyacrylamide using continuous and pulsed electric fields

This paper presents results on the separation of DNA restriction fragments by high performance capillary electrophoresis (HPCE). Capillaries containing polyacrylamide with low amounts of crosslinking agent (i.e. 0.5% C) were first studied. The greater molecular accessibility offered with columns of low crosslinking, relative to higher crosslinked gels (e.g. 5% C), permitted high efficiency separations of double stranded DNA fragments up to 12,000 base pairs in length. Capillaries containing no crosslinking agent, i.e. linear polyacrylamide, were then examined. Ferguson plots (i.e. log mobility vs. %T) were used to assess the size selectivity of linear polyacrylamide capillaries. In another study, it was determined that the relative migration of DNA species was a strong function of applied electric field and molecular size. Lower fields yielded better resolution than higher fields for DNA molecules larger than about 1000 base pairs, albeit at the expense of longer separation time. Based on these results, we have examined pulsed field HPCE and have demonstrated the use of this approach to enhance separation.

Separation and analysis of DNA sequence reaction products by capillary gel electrophoresis

This paper demonstrates the potential of capillary gel electrophoresis with laser induced fluorescence detection as a tool for DNA sequence determination. Both synthetic oligonucleotides and single-stranded phage DNA were utilized as templates in the standard chain termination procedure. Primer molecules were tagged at the 5' end with the fluorescent dye, JOE. First, baseline resolution of a dA extended primer from 18 to 81 bases long, a total of 64 fragments, was observed. A second synthetic template was designed to yield alternating stretches of dA and dT extensions of the primer. Thirdly, the sequence reaction products from a synthetic oligonucleotide template containing all four bases was analyzed in four independent runs, one for each of the four base-specific reactions. In all cases, the expected number and patterns of peaks were observed by capillary gel electrophoretic analysis. Finally, separation of sequence reaction products generated with single-strand M13mp18 phage DNA as template exhibited baseline resolution of fragments differing in length by a single nucleotide and from 18 to greater than 330 bases total length.

Generation and use of site-specific antibodies to serum amyloid A for probing amyloid A development

Serum amyloid A (SAA) is an acute phase reactant and the putative precursor of an amyloid fibril protein (AA). During amyloidogenesis in mice, the C-terminal portion of SAA that consists of 28 amino acids is cleaved off to produce the 75 amino acid AA. Of three known isotypes of SAA, SAA2 has been identified as amyloidogenic. For differential immunologic recognition of SAA and AA, antisera were generated in rabbits against AA protein and a synthetic peptide corresponding to the C-terminal (amino acids 84 to 103) of murine SAA2. The anti-AA antiserum reacted with AA and SAA, but the anti-peptide antiserum reacted with SAA only. Immunohistochemically anti-peptide antiserum predominantly stained the rims of murine amyloid deposits. In contrast, anti-AA antiserum generated an overall homogeneous staining of amyloid deposits. The data lend support to a view that SAA are concentrated in the vicinity of the surrounding cells (mostly macrophages) where they are processed to AA, or that SAA are deposited initially as components of the amyloid fibrils onto the outside margin of amyloid deposits and the C-terminus is cleaved off as maturation of the amyloid fibril progresses.

Generation and use of site-specific antibodies to serum amyloid A for probing amyloid A development

Serum amyloid A (SAA) is an acute phase reactant and the putative precursor of an amyloid fibril protein (AA). During amyloidogenesis in mice, the C-terminal portion of SAA that consists of 28 amino acids is cleaved off to produce the 75 amino acid AA. Of three known isotypes of SAA, SAA2 has been identified as amyloidogenic. For differential immunologic recognition of SAA and AA, antisera were generated in rabbits against AA protein and a synthetic peptide corresponding to the C-terminal (amino acids 84 to 103) of murine SAA2. The anti-AA antiserum reacted with AA and SAA, but the anti-peptide antiserum reacted with SAA only. Immunohistochemically anti-peptide antiserum predominantly stained the rims of murine amyloid deposits. In contrast, anti-AA antiserum generated an overall homogeneous staining of amyloid deposits. The data lend support to a view that SAA are concentrated in the vicinity of the surrounding cells (mostly macrophages) where they are processed to AA, or that SAA are deposited initially as components of the amyloid fibrils onto the outside margin of amyloid deposits and the C-terminus is cleaved off as maturation of the amyloid fibril progresses.

Amyloid enhancing factor-loaded macrophages in amyloid fibril formation

Amyloid enhancing factor (AEF) is believed to be a key agent that triggers the second (deposition) phase of amyloidogenesis. However, the target cells of AEF activation and their function after the activation have not yet been clearly identified. We found that peritoneal resident cells from amyloidotic mice contained very high AEF activity. With a simultaneous subcutaneous injection of 1.0 ml of the casein-adjuvant emulsion, an intravenous injection of 10,000 cells was consistently capable of inducing amyloidosis in a recipient mouse in 72 hours. After 2-hour cultures, the major AEF activity was found in the adherent cells (macrophages). An intravenous injection of 5 to 10 million of the live macrophages with the casein-adjuvant injection caused amyloid deposits in the recipient not only in the spleen and the liver but also in the lung (an extremely rare site of AA amyloid deposition). We have interpreted this finding to indicate that the injected AEF-loaded macrophages, while still residing in the lung and exposed to the blood stream, processed SAA to form amyloid. We further tested this postulate in an in vitro system. In a 4-day culture of the AEF-loaded macrophages in a medium containing SAA-rich mouse serum, small masses (less than 15 microns in diameter) of Congo red positive substance were observed scattered adjacent to or surrounded by the macrophages. The present observations lend strong credence to the conclusion that AEF-loaded macrophages are fully capable of processing SAA to AA and further to amyloid fibrils, and that they indeed play a role in the second phase of amyloidogenesis in vivo.

Glycosaminoglycans of the hemodialysis-associated carpal synovial amyloid and of amyloid-rich tissues and fibrils of heart, liver, and spleen

Significant amounts of glycosaminoglycans (GAGs) were found in amyloid fibril preparations. Using two-dimensional electrophoresis to fractionate GAG mixtures, we quantified and identified for the first time the GAGs of the fibrils from carpal synovium of patients with amyloid associated with chronic hemodialysis. The total GAG content was small, but the GAG distribution (high relative content of chondroitin sulfate and hyaluronic acid and lack of the other GAGs) was unique, unlike that for the other amyloid fibril preparations. The amyloid-rich heart, liver, and spleen tissues, as well as the fibrils isolated from these tissues of patients with systemic forms (primary amyloid and secondary amyloid) of amyloid disease, were also analyzed for GAGs. Fibrils from heart tissue of a patient with primary amyloidosis, now examined for the first time, contained four major GAGs (chondroitin sulfate, dermatan sulfate, hyaluronic acid, and heparan sulfate).

Glycosaminoglycans of the hemodialysis-associated carpal synovial amyloid and of amyloid-rich tissues and fibrils of heart, liver, and spleen

Significant amounts of glycosaminoglycans (GAGs) were found in amyloid fibril preparations. Using two-dimensional electrophoresis to fractionate GAG mixtures, we quantified and identified for the first time the GAGs of the fibrils from carpal synovium of patients with amyloid associated with chronic hemodialysis. The total GAG content was small, but the GAG distribution (high relative content of chondroitin sulfate and hyaluronic acid and lack of the other GAGs) was unique, unlike that for the other amyloid fibril preparations. The amyloid-rich heart, liver, and spleen tissues, as well as the fibrils isolated from these tissues of patients with systemic forms (primary amyloid and secondary amyloid) of amyloid disease, were also analyzed for GAGs. Fibrils from heart tissue of a patient with primary amyloidosis, now examined for the first time, contained four major GAGs (chondroitin sulfate, dermatan sulfate, hyaluronic acid, and heparan sulfate).

A new mutation causing familial amyloidotic polyneuropathy

The DNA from an individual with familial amyloidotic polyneuropathy was examined. It did not possess any of the mutations which have previously been associated with familial amyloidotic polyneuropathy. However, a novel 7.0 kb Sph I restriction fragment was discovered, and the mutation creating it was localized to exon 3 of the transthyretin gene. This mutation was inherited from a parent, and may result in an amino acid substitution for glu89, his90 or ala91. The patient's transthyretin has a lower pI than normal transthyretin.

High-performance capillary electrophoresis in the biological sciences

High-performance capillary electrophoresis (HPCE), the instrumental approach to electrophoresis, is a method undergoing rapid development at the present time. There is a high expectation that HPCE will become a widely applicable tool within the biochemical community. This review presents principles and instrumentation followed by typical applications of HPCE in the biological area. In the instrumentation area, particular attention is paid to current and future detectors, including laser-induced fluorescence and HPCE-mass spectrometry. In the applications section, both peptide or protein and oligonucleotide high-resolution separations are described for open-tube and polyacrylamide gel capillary columns. The use of isoelectric focusing and electrokinetic chromatography to manipulate separation is also presented. Future directions of methodology are suggested, and it is predicted that in the next few years HPCE will become a complementary tool to liquid chromatography and slab gel electrophoresis.

Peripheral neuropathy as an early marker of AL amyloidosis

Fifty-one of 146 patients with primary amyloid deposits of light-chain origin (AL) examined between 1972 and 1986 were found to have peripheral neuropathy as part of their systemic amyloidosis. Peripheral neuropathy was the presenting symptom in 11 patients, and it was a later symptom or an incidental physical examination finding at the time of amyloid workup in 40 additional patients. The median duration of time from first symptom to the diagnosis of primary amyloidosis was longer in those whose first symptom was neuropathy (48 months vs 12 months). In addition, survival time after diagnosis for these patients was significantly longer (at least 35 months vs 16 months). Peripheral neuropathy is not an uncommon symptom of primary amyloidosis and may mark the onset of the disease process years before infiltration of vital structures of the heart, kidneys or gastrointestinal tract leads to failure and a subsequent downhill course. Appreciating amyloid disease at this early stage may widen the potential therapeutic window.

Sensitivity, specificity, and predictive value of abdominal fat aspiration for the diagnosis of amyloidosis

Samples of abdominal fat aspirates from 73 patients were sent to us for staining and interpretation. Ten samples were positive for amyloid. We calculated the sensitivity, specificity, and predictive value of the procedure based on the findings and the clinical information and other biopsy data about these patients. Using the results from more traditional biopsies as the "gold standard," sensitivity was 57%, specificity was 100%, and the predictive value was 100% for positive findings in the abdominal fat aspirate. Although the sample size in this study was relatively small, the procedure was found to be a minimally invasive test of high clinical utility.