Family A and family B DNA polymerases are structurally related: evolutionary implications

In order to establish the evolutionary relationship between the family A and B DNA polymerases, we have closely compared the 3'-->5' exonuclease domains between the Klenow fragment of E.coli DNA polymerase I (a family A DNA polymerase) and the bacteriophage PRD1 DNA polymerase, the smallest member of the DNA polymerase family B. Although the PRD1 DNA polymerase has a smaller 3'-->5' exonuclease domain, its active sites appear to be very similar to those of the Klenow fragment. Site-directed mutagenesis studies revealed that the residues important for the 3'-->5' exonuclease activity, particularly metal binding ligands for the Klenow fragment, are all conserved in the PRD1 DNA polymerase as well. The metal binding ligands are also essential for the strand-displacement activity of the PRD1 DNA polymerase. Based on these results and the studies by others in various systems, we conclude that family A and B DNA polymerases, at least in the 3'-->5' exonuclease domain, are structurally as well as evolutionarily related.

[Cochlear implants in children]

A multichannel cochlear implant was performed in 8 children, and the following results were obtained. The surgical procedures were not as difficult as in adults, and there were few postoperative complications. The results of testing postoperative speech comprehension ability were examined in three children whose course was followed for more than one year postoperatively. Some patients had good speech comprehension ability postoperatively, and we expect to continue performing cochlear implant in children. Postoperative rehabilitation takes longer. The cooperation of physicians, audiologists, speech therapists, school teachers and family members is essential, and establishing a cochlear implant center for children would be desirable.

Intramyocardial angiomyolipoma

We report a case of cardiac angiomyolipoma in a 48-year-old woman who went to the hospital because of shortness of breath. Cardiac ultrasonography showed a right atrial mass, which was surgically removed. Pathologic examination revealed a 6-cm-diameter, dome-shaped mass composed of a mixture of blood vessels, smooth muscle, and fat. Because of its distinctive morphology and location, we diagnosed it as an intramyocardial angiomyolipoma. There was no evidence of tuberous sclerosis. Since excision of the mass, the patient has remained well without recurrence for 20 months. Angiomyolipomas usually develop in the kidney; extrarenal occurrence is rare. To date, no case of a cardiac angiomyolipoma has been reported in the English literature. The histogenesis of angiomyolipoma is uncertain, but it is most likely hamartomatous in nature.

[Cochlear implants for adult prelingually deaf patients]

We have performed cochlear implants on 6 adult prelingually deaf patients and obtained the following results. 1) The speech comprehension ability of the adult prelingually deaf patients was poorer than in postlingually deaf patients, but some patients showed better results than expected. 2) The adult prelingually deaf patients required a longer period of rehabilitation than the postlingually deaf patients. There were considerable variations in performance among the adult prelingually deaf patients.

Mutagenesis of a highly conserved lysine 340 of the PRD1 DNA polymerase

All known family B DNA polymerases contain a conserved region of amino acids, KX6-7YG, which appears to be correspond to the 'finger' alpha helix O of the Klenow fragment of E. coli DNA polymerase I, a family A DNA polymerase. Toward the goal of establishing the evolutionary relationship between the family A and B DNA polymerases, we have employed site-directed mutagenesis to access the functional role of the invariant amino acid lysine-340 of the PRD1 DNA polymerase. We have replaced the lysine-340 with three amino acids: histidine, asparagine and glutamic acid, respectively. Mutant DNA polymerases were overexpressed and purified to near homogeneity. Our results showed that the modification of the lysine-340 of the PRD1 DNA polymerase abolishes the polymerase activity without affecting the 3' to 5' exonuclease activity. These results support the proposal that the KX6-7YG motif of the family B DNA polymerases may be analogous to the KX7YG motif of the family A DNA polymerases, suggesting that two family DNA polymerases share a common ancestor.

Purification and characterization of PRD1 DNA polymerase

A small lipid-containing bacteriophage PRD1 encodes a DNA polymerase that utilizes a protein primer for the initiation of DNA replication. The purification of the PRD1 DNA polymerase has been hampered by the insolubility of the overexpressed enzyme in Escherichia coli cells. We have developed a simple and rapid procedure for purification of the overexpressed PRD1 DNA polymerase. This method is based on guanidine hydrochloride denaturation and renaturation of the insoluble PRD1 DNA polymerase overexpressed in E. coli containing the recombinant plasmid pEJG. The purified DNA polymerase was extensively characterized and found to be indistinguishable from the normal soluble PRD1 DNA polymerase as judged by enzymatic properties. These properties include: protein-primed initiation of PRD1 DNA replication, strand-displacement DNA synthesis, DNA polymerase processivity, 3' to 5' exonuclease activity and filling-in repair type DNA synthesis. Furthermore, the kinetic parameters determined for dNTPs and primer-terminus were of the same order of magnitude. The availability of a simple purification procedure for the PRD1 DNA polymerase should permit detailed structure-function analysis of this enzyme.

[A case of mitral valve replacement with chronic idiopathic thrombocytopenic purpura after high-dose immunoglobulin infusion]

A 60-year-old female patient diagnosed as having mitral stenosis with chronic idiopathic thrombocytopenic purpura (ITP), with a platelet count of 6.8 x 10(4)/mm3, was scheduled to undergo mitral valve replacement. High-dose immunoglobulin infusion (400 mg/kg/day for five days) was begun four days before the operation and increased the platelet count to 9.1 x 10(4)/mm3 just before the operation. Intraoperative hemostasis was excellent, and the postoperative course was uneventful. High-dose immunoglobulin therapy appears to be a first choice for controlling hemorrhagic tendency in ITP patients undergoing heart surgery.

Effect of caloric stimulation on primary vestibular fibers originating from otolith organs in the guinea pig

The influence of caloric stimulation on the primary vestibular fibers originating from the otolith organ was investigated in the guinea pig. Firing rates were recorded from single vestibular neurons in the superior vestibular (Scarpa's) ganglion which were identified physiologically as originating from the otolith organs, mainly from the utricles. Eighty-six percent of the neurons responded to caloric stimulation. Neurons with a high coefficient of variation of firing regularity reacted more sensitively to tilting and also had a tendency to react more sensitively to caloric stimulation. There was a tendency for neurons with increased firing rates in response to ipsilateral tilting to have increased firing rates to warm stimulation, while neurons whose rates increased to contralateral tilting had increased firing rates to cold stimulation. These results indicate that the otolith organs have the same unidirectional tendency to caloric simulation with results comparable to optimal tilting directions.

The mechanism of speech perception in patients with a multichannel cochlear implant

The mechanism of speech perception in patients with a multichannel cochlear implant was investigated by administering vowel, consonant, and speech recognition tests, and comparing sound spectrograms with the activities recorded from the cochlear implant electrodes. Vowel recognition was found to be adequate, but consonant recognition was poor. Although the cochlear hair cells of such patients are known to be functionally damaged, the cochlear nerve was found to have the capacity to characterize frequency. The signals from the implanted device were very simple compared with those from the normal cochlea; however, the patients could nevertheless understand speech well after cochlear implantation.

Automatic detection of P300 in single sweep records of auditory event-related potential

In the conventional recording of event-related potentials (ERPs) by the "oddball" paradigm, the subject may employ different strategies for processing one stimulus from the other even within the same session because of variable psychological state. Hence, "averaging" may not necessarily be suitable for recording ERP. We have therefore established a method for single trial recording of auditory ERPs by processing the EEG data through discrete Fourier transform followed by inverse discrete Fourier transform with the low pass filter of 8 Hz (digital filter). Each single sweep response of the processed data was visually evaluated as to whether it contained P300 or not by three investigators who were made completely blind with respect to the category of each response. As the result, a positive peak at a latency of 200-500 ms was recognized in the single sweep responses to target stimuli at a significantly greater frequency (40-60%) than in those to nontarget stimuli (0-18%). Then a new method for the automatic detection of P300 was established based on the data of 11 subjects belonging to the training group, by taking into account, in addition to the correlation coefficient analysis in which the template was computed specifically for each subject, other criteria with respect to the amplitude and waveforms, so that a good agreement with the results of visual inspection as to the presence or absence of P300 could be achieved for both target and nontarget responses. This automatic analysis method was successfully applied to five other subjects of the test group. The peak latency and amplitude of the detected positive peaks significantly varied among single target responses even within the same session. The reaction time significantly correlated positively with the peak latency of the detected positive peaks and negatively with the amplitude of those peaks, supporting the usefulness of the present method.

Improvement of mitomycin C- and cyclophosphamide-induced thrombocytopenia and leucocytopenia by prior treatment with deoxyspergualin in dogs

Deoxyspergualin (DGS) is a new immunosuppressant which has shown inhibitory haemopoietic activity. We investigated the myeloprotective effect of DSG against the haemopoietic injury of mitomycin C (MMC) or cyclophosphamide (CYC) by measuring peripheral blood cell numbers in dogs. DSG given at 5 mg/kg on days 3, 2 and 1 before, or at 10 mg/kg on either days 2 and 1 before or on day 1 before and the day of injection of MMC at 0.25 mg/kg ameliorated both the thrombocytopenia and leucopenia caused by MMC. This ameliorative effect was more evident on platelet counts than on white blood cell counts. In addition, the leucopenia and thrombocytopenia induced by a single injection of CYC at 10 mg/kg was also ameliorated by prior DSG administration. These findings suggest that DSG may be useful in protecting against the haemopoietic damage induced by chemotherapeutic agents in the treatment of cancer.

A simple method for determination of stereospecificity of aminotransferases for C-4' hydrogen transfer of the coenzyme

A simple method was established for determination of the stereospecificity of C-4' hydrogen transfer of the coenzymes (pyridoxal and pyridoxamine). The method is based on the findings that aspartate aminotransferase of pig heart and D-amino acid aminotransferase of Bacillus sp. YM-1 catalyze the abstraction of the pro-S and pro-R proton at C-4' of pyridoxamine, respectively. Pyridoxal is a poor coenzyme, but readily released from the enzyme. It reacts in 3H2O with a substrate amino acid and an apo-aminotransferase whose stereospecificity for C-4' hydrogen transfer is to be determined. The resultant pyridoxamine which is tritiated at C-4' is incubated with an apo form of aspartate aminotransferase or D-amino acid aminotransferase and a substrate, alpha-keto acid. The stereospecificity for the C-4' hydrogen transfer examined is determined by measurement of radioactivity retained in the pyridoxal formed. We showed by means of this method that C-4' hydrogen transfer of coenzyme occurs on the si face of the external Schiff base in the transamination reactions of two aspartate aminotransferases of Bacillus sp. YM-2 and Escherichia coli, and aromatic amino acid aminotransferase of E. coli.

Tinnitus suppression by electrical stimulation of the cochlear wall and by cochlear implantation

Some recent studies have reported on tinnitus suppression by electrical stimulation of the cochlear wall and by cochlear implant. In the present study, the degree of tinnitus in cochlear implant candidates was determined and the effects of promontory stimulation and cochlear implantation on tinnitus were investigated. Of the cochlear implant candidates, all of whom were either severely hearing impaired or totally deaf, 87% experienced tinnitus. When electrical stimulation was applied to the cochlear wall (promontory stimulation test), tinnitus was abolished in 23% and improved in 46% of the patients. Thus, electrical stimulation of the cochlear wall effectively suppressed tinnitus in 69% of the patients. Following cochlear implantation, tinnitus was abolished in 35% and decreased in 42%. Thus, intracochlear electrical stimulation was effective for treatment of tinnitus in 77% of the patients. The suppression of tinnitus continued for several hours after the patients switched off the implant device. In 60% of the patients whose tinnitus was suppressed or abolished after the cochlear implant surgery, tinnitus was also suppressed in the contralateral ear.

[A case report of tricuspid replacement for the acquired tricuspid stenosis at the time of reoperation]

A 57-year-old woman, who underwent aortic valve replacement and open mitral commissurotomy nine years ago, was admitted with congestive heart failure due to mitral regurgitation and tricuspid regurgitation, for which we planned mitral valve replacement and tricuspid annuloplasty. Intraoperatively, the orifice of tricuspid valve was stenosed like fish-mouth, which we attempted to make commissurotomy and modified Kay's annuloplasty, but failed to decrease the central regurgitation. A CarboMedics 23 mm prosthesis was implanted in the mitral position and a Capentier-Edwards 29 mm in the tricuspid position. She had recovered from congestive heart failure postoperatively, no regurgitant flow was detected in right ventriculography.

Prediction of systemic fungal infection in allogeneic marrow recipients: impact of amphotericin prophylaxis in high-risk patients

PURPOSE

To identify risk factors that might predict for systemic fungal infections in marrow transplant recipients within the first 100 days and to assess the efficacy of low-dose amphotericin B used as prophylaxis for candidemia and infection with invasive Aspergillus species in patients at risk.

PATIENTS AND METHODS

A retrospective analysis of transplant outcomes for 331 allogeneic marrow recipients transplanted between 1983 and 1989 was performed to identify patients who might be at increased risk of fungal infection. Factors analyzed included disease, remission status, transplant regimen, graft-versus-host disease (GVHD) prophylaxis, duration of neutropenia, and development of GVHD. A trial of low-dose amphotericin (5 to 10 mg/d) begun on day +1 and continuing for 2 to 3 months posttransplant was begun in 1987 to evaluate its utility in reducing systemic mycoses.

RESULTS

There were 18 episodes of candidemia and 18 systemic mycoses documented by blood or tissue culture or by biopsy. The initiation of high-dose (0.5 to 1 mg/kg/d) corticosteroids early as a component of GVHD prophylaxis in 1986 was identified as the most important risk factor for fungal infections, with a sixfold increase in infections as compared with the previous GVHD regimen (P < .0001); this was despite a significant decrease in the incidence of grade II to IV GVHD (7% v 43%; P = .0001). Low-dose amphotericin B initiated before the start of high-dose corticosteroid GVHD prophylaxis reduced the incidence of fungal infections from 30% to 9% (P = .01) without renal toxicity. Cyclosporine levels were lower in the patients who received amphotericin, leading to an increase in the rate of GVHD to 19% (P = .02). Controlling for GVHD prophylaxis, prolonged neutropenia (P = .00), and grade II to IV GVHD (P = .01) were also identified as risk factors for fungal infection.

CONCLUSION

Amphotericin B can be used in low doses as prophylaxis for fungal infections early in the posttransplant course. However, cyclosporine doses need to be monitored to maintain target levels.

Determination of the origin of autonomic nerves of the tongue using horseradish peroxidase as tracer

Autonomic innervation of the tongue was investigated in cats using the horseradish peroxidase retrograde tracing method. The tongue was found to be innervated by sympathetic fibers originating in the ipsilateral superior cervical ganglion, but not by those originating in the middle cervical ganglion or stellate ganglion. The tongue was also innervated by fibers originating in the ipsilateral pterygopalatine ganglion, suggesting that this innervation is parasympathetic.

Suppression of tinnitus by cochlear implantation

INTRODUCTION

Transcutaneous and transpromontory electrical stimulation has been described for the treatment of tinnitus. Based on these observations, we postulate that cochlear implantation may relieve tinnitus.

METHOD

Twenty patients who underwent cochlear implantation since 1987 were studied. Preimplantation tinnitus was documented and quantified. The change in tinnitus after implantation was investigated.

RESULT

Before cochlear implantation, 90% of the patients experienced tinnitus. Electrical stimulation of the promontory resulted in relief of tinnitus in 72% of the patients. After cochlear implantation, tinnitus was abolished in 44% and decreased in 39%, for an overall improvement in 83%.

CONCLUSION

Cochlear implantation has the added benefit of tinnitus suppression in the majority of patients. The mechanism of this suppression remains uncertain. However, this information may be valuable in structuring subsequent treatment programs for patients with tinnitus.

Somatosensory event-related potentials (ERPs) in patients with different types of dementia

Somatosensory ERPs and short latency somatosensory evoked potentials (SSEPs) were studied in patients with dementia of the Alzheimer type (DAT), those with vascular dementia, demented and non-demented patients with Parkinson's disease, and healthy control subjects. In control subjects, latencies of N140, P200, N240 and P300 components increased with age at a rate of 0.2, 0.2, 0.6 and 1.5 msec/year, respectively. Patients with DAT and demented patients with Parkinson's disease had normal SSEPs as well as normal P100, and N140 latencies, but patients with vascular dementia showed prolonged N140 and P200 latencies in addition to a prolonged central conduction time (CCT). Analysis of N140 and P200 components of somatosensory ERPs may be important for evaluation of patients with vascular dementia. In patients with DAT, those with vascular dementia and demented patients with Parkinson's disease, the P300 latency was significantly prolonged compared with that in age-matched control subjects. However, the P300 latency did not show any significant differences among the groups of demented patients.

Disbanding a multidisciplinary clinic: effects on the health care of myelomeningocele patients

A multidisciplinary clinic for the evaluation and care of children with central nervous system malformations was established at our hospital in 1963 and disbanded in 1988. Three years later, a retrospective telephone survey of myelomeningocele patients (n = 87) was used to identify the effect of clinic closing on the health and care of these patients. After the clinic was disbanded, 45-66% of myelomeningocele patients failed to have regular medical and specialty care, despite the continued availability of the same specialty care in the same location. The most significant correlation was that older patients had less frequent care; this failure in health care utilization was not related to the patients' insurance status. This lack of care is not benign. An increase in serious morbidity, including amputation and nephrectomy, was detected in those patients with the least follow-up, but not in the control group. A significant problem with coordination of the patients' care exists; neither the patient, the family, nor the local physician assumes the duties of coordinator of care. This review indicates that if a multidisciplinary clinic is disbanded, a large proportion of patients will fail to maintain adequate medical follow-up, and that significant morbidity can occur within several years. It is unrealistic to expect the continuation of effective care by merely maintaining the individual services of the disbanded clinic, without some coordinator of care.

Sialosylcholesterol effects on reconstitution of microfilament and glia filament

The effects of alpha-sialosylcholesterol (alpha-SC) on formation of either microfilament or glia filament of rat astrocytes were investigated using a reconstitution system. Polymerization of the depolymerized microfilament preparation that had been extracted from a crude cytoskeletal fraction of rat astrocytes, in the presence of 100 mM KCl and 10 mM MgCl2, was suppressed in a dose-dependent manner by alpha-SC. alpha-SC inhibited polymerization of G-actin in a similar manner. The intensity of alpha-SC inhibition of G-actin polymerization was as great as that of microfilament polymerization, suggesting that the inhibition of microfilament polymerization by alpha-SC was due to the direct action of alpha-SC on actin, the main component of microfilament. alpha-SC depolymerized partly the polymerized microfilament preparation, which resembled F-actin (microfilament-like filaments). alpha-SC suppressed, in a dose-dependent manner, polymerization of a glia filament preparation that had been extracted from astrocyte cytoskeletons in the presence of phalloidin. An increase in the amount of added alpha-SC (up to 15 microM) decreased the amount of the larger glia filament-like filaments, which were 10 nm thick and centrifuged down at 16,000 g for 30 min, and increased that of smaller ones precipitated only after centrifugation at 100,000 g for 1 h. The lower the concentration of the depolymerized glia filament extract, the greater was the inhibition by alpha-SC of the polymerization. alpha-SC repressed polymerization of vimentin, the dominant component of glia filament. Vimentin polymerization was more strongly inhibited by alpha-SC than polymerization of glia filament was.(ABSTRACT TRUNCATED AT 250 WORDS)