Temporal non-linearities of the cochlear amplifier revealed by maximum length sequence stimulation

OBJECTIVES

The objective of this study was to examine whether temporal non-linearities of the cochlear amplifier, as reflected by otoacoustic emissions (OAEs), exist and are distinct from any recording system non-linearities.

METHODS

Maximum length sequence stimulation, at various stimulus rates, was used to evoke OAEs from normally hearing subjects. Recordings from a 2cc cavity were also made. The data were analyzed to obtain the linear response and estimates of the slices of the 2nd and 3rd order Volterra kernels. This provided a measure of two and 3 click non-linear temporal interactions, respectively.

RESULTS

The results showed that temporal non-linearities of OAEs do exist, are stable and repeatable within individuals and have properties that differ from those shown by the conventional linear response. Whilst some of the non-linear response properties conformed to the expected pattern, of increasing amplitude with increase in stimulus rate, there are some areas in which they show an unpredicted complexity.

CONCLUSIONS

Whilst system non-linearities could be found, there was no difficulty in distinguishing between the physiological and system non-linear components. New areas of research and application may result from the use of these new OAE responses.

Inhibition of Escherichia coli respiratory enzymes by the lactoperoxidase-hydrogen peroxide-thiocyanate antimicrobial system

AIMS

The lactoperoxidase-hydrogen peroxide-thiocyanate antimicrobial system (LPAS) is known to inhibit bacterial respiration. In the present study, several respiratory enzymes of Escherichia coli were compared in terms of their susceptibility to the LPAS.

METHODS AND RESULTS

Exposure of E. coli to the LPAS, upon which 99.6% of the bacteria were killed, resulted in the following percentage of inactivation of substrate-specific membrane oxidases: succinate (94.2%) > NADH (84.6%) > glycerol-3-phosphate (67.8%) > DL-lactate (64.1%). With the same treatment, substrate-specific membrane dehydrogenases were inactivated as follows: succinate (99.1%) > DL-lactate (53.8%) > glycerol-3-phosphate (45.0%) > NADH (36.8%). Terminal oxidase, however, measured using a ubiquinone analogue (2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone) after reduction, was only 21.4% inactivated by the LPAS.

CONCLUSION

These data suggest that dehydrogenases are the primary targets of the LPAS in the respiratory chain of E. coli.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study has determined for the first time the primary targets of LPAS in the bacterial respiratory chain.

Mutations affecting the calcium-binding site of myeloperoxidase and lactoperoxidase

Both myeloperoxidase (MPO) and lactoperoxidase (LPO) contain high affinity bound calcium, which has been suggested to play a structural role. Asp-96 in MPO, a residue next to the histidine distal from the heme prosthetic group, has been assigned to the calcium-binding site of the enzyme by X-ray crystallography. Multiple sequence alignment of known animal peroxidases has revealed that the calcium-binding site is highly conserved. In this study, we replaced Asp-96 in MPO and the counterpart Asp-227 in LPO both with Ala by site-directed mutagenesis. The level of peroxidase activity in insect cells infected with recombinant baculoviruses and their culture supernatants was reduced to virtually zero as a result of these mutations. Immunoblotting revealed that these mutant peroxidases were expressed in the cells but not secreted as effectively as the wild-type enzymes. Our findings suggest that a functional calcium-binding site is essential for the biosynthesis of active animal peroxidases.

[Periodontal plastic surgery as a regenerative medical science]

A regenerative medical science is the medical field of the next generation for a human's tissue and organ reproducing original structure and an original function. On the other hand, periodontal plastic surgery (PPS) defines as surgical procedures performed to correct or eliminate deformities of the gingival or alveolar mucosa. Therefore, PPS is considered to be one field in a regenerative medical science. In addition to the free soft tissue graft from the former, a guided tissue regeneration (GTR) and/or enamel matrix derivative has come to be used. This paper displays and explains clinical cases about the PPS from the standpoint of a regenerative medical science.

Radioactivity induced in a 2.5 GeV electron beam dump

The saturation activity of residual nuclei was estimated based on measurements when 2.5 GeV electron beams were totally absorbed in thick Al, Fe, Cu and Pb. A calculation was also made for a beam dump from 0.1 to 10 GeV using the EGS4 and PICA95 Monte Carlo codes. Above 1 GeV, the activity was constant in units of MBq.W-1. The gamma ray dose rates from the targets were calculated using these data.

DNA electrophoresis on a flat surface

We report a new approach for performing DNA electrophoresis. Using experimental studies and molecular dynamics simulations, we show that a perfectly flat silicon wafer, without any surface features, can be used to fractionate DNA in free solution. We determine that the ability of a flat surface to separate DNA molecules results from the local friction between the surface and the adsorbed DNA segments. We control this friction by coating the Si surface with silane monolayer films and show that it is possible to systematically change the size range of DNA that can be separated.

[Three infants who suddenly became unwilling to stand up presumably due to acute cerebellar ataxia]

We reported here three infants aged 11 to 12 months who, according to their parents, suddenly became unwilling to stand up. All the patients had barely achieved the ability to stand or to walk at the time of the illness. The symptom developed relatively acutely in the winter months from 1997 to 1998 with a probable preceding infection. On examination, no paralysis of the lower extremities was observed, and muscle weakness was minimal. There were neither violent tremors, nystagmus, nor sensory disturbance. Orthopaedic disorders were considered unlikely. Biochemical examinations of the serum were not diagnostic, and imagings of the central nervous system were normal. Spinal tap revealed mild cerebrospinal fluid pleocytosis in two of the patients. All the children showed almost complete recovery without any medication during the following period of 2 days to 2 months. Although no definite signs of ataxia were recognized in the three patients, a diagnosis of acute cerebellar ataxia was considered to be appropriate. Mild, infantile acute cerebellar ataxia may be overlooked because of the obscure complaints of the parents and the difficulty in performing a thorough neurological examination of infants.

cAMP response element-mediated gene transcription is upregulated by chronic antidepressant treatment

Regulation of gene transcription via the cAMP-mediated second messenger pathway has been implicated in the actions of antidepressant drugs, but studies to date have not demonstrated such an effect in vivo. To directly study the regulation of cAMP response element (CRE)-mediated gene transcription by antidepressants, transgenic mice with a CRE-LacZ reporter gene construct were administered one of three different classes of antidepressants: a norepinephrine selective reuptake inhibitor (desipramine), a serotonin selective reuptake inhibitor (fluoxetine), or a monoamine oxidase inhibitor (tranylcypromine). Chronic, but not acute, administration of these antidepressants significantly increased CRE-mediated gene transcription, as well as the phosphorylation of CRE binding protein (CREB), in several limbic brain regions thought to mediate the action of antidepressants, including the cerebral cortex, hippocampus, amygdala, and hypothalamus. These results demonstrate that chronic antidepressant treatment induces CRE-mediated gene expression in a neuroanatomically differentiated pattern and further elucidate the molecular mechanisms underlying the actions of these widely used therapeutic agents.

PCR cloning and baculovirus expression of human lactoperoxidase and myeloperoxidase

Lactoperoxidase (LPO) and myeloperoxidase (MPO) have been identified previously in human milk. These peroxidases have antimicrobial activity and presumably contribute to the protective functions of milk. In this study, we amplified genes encoding LPO and MPO from human mammary gland cDNA by the polymerase chain reaction (PCR). These genes were expressed in a baculovirus-insect cell system. Peroxidase activity was observed in the culture supernatant of Tricoplusia ni cells infected with the recombinant viruses and the levels increased upon addition of delta-aminolevulinic acid. Purified recombinant human LPO and MPO, both with a molecular mass of about 80 kDa, showed properties similar to bovine LPO and human MPO, respectively, in terms of absorption spectrum, sensitivity to dapsone, specificity for chloride ions, and reactivity with anti-bovine LPO or anti-MPO antibodies. Our data suggest that this expression system is useful for studying the catalytic mechanism and biological significance of these human peroxidases.

The influence of controlled occlusal overload on peri-implant tissue. Part 3: A histologic study in monkeys

The influence of experimental occlusal overload on peri-implantitis in monkeys (Macaca fascicularis) has been examined to explain the pathology of the disease that develops in the tissue around osseointegrated implants. In the first article of this series, it was reported that bone resorption was not observed around implants when occlusal trauma was produced by a super-structure that was in supraocclusal contact with an excess occlusal height of approximately 100 microns, provided there was no inflammation in the peri-implant tissue. In the second part of the study, experimental inflammation was created in the peri-implant tissue, and occlusal overload was produced by a superstructure with an excess occlusal height of 100 microns. Notable bone resorption was observed around the implant with the passage of time. These results suggested that, in addition to the control of inflammation in peri-implant tissue, traumatic occlusion may play a role in bone breakdown around the implant. In the present study, while the peri-implant tissue was kept in an inflammation-free state, bone level changes around the implants were investigated when various levels of traumatic force were exerted. The supraoccluding prostheses were defined as excessively high by 100 microns, 180 microns, and 250 microns, respectively. The heights were determined with an image analysis device, and the bone responses around the implants induced by the traumatic forces were investigated. The results showed that bone resorption around implants tended to increase with 180 microns or more excessive height of the superstructure. This suggests that the threshold of excessive height of the superstructures at which peri-implant tissue breakdown may start is approximately 180 microns. It is also suggested that there is a possibility of bone resorption around the implants caused by excess occlusal trauma, even when there is no inflammation in peri-implant tissue.

Identification of lactoperoxidase in mature human milk

Myeloperoxidase (MPO) derived from milk leukocytes and lactoperoxidase (LPO) secreted from the mammary gland have been identified previously in human colostrum. These peroxidases are known to play host defensive roles through antimicrobial activity. The goals of this study were to measure the peroxidase activity in mature human milk and to characterize the enzyme responsible for the activity. As determined using 3,3',5,5'-tetramethylbenzidine as substrate, whey prepared from human milk samples obtained 1 and 5 months postpartum showed levels of peroxidase activity equivalent to 0.13 +/- 0.18 and 0.24 +/- 0.21 microg/mL bovine LPO (bLPO; n = 13), respectively. Whey from early milk was fractionated into two peaks of peroxidase activity by cation-exchange chromatography; the peroxidase in the first peak was sensitive to dapsone, which is an inhibitor of LPO, whereas the second peroxidase was not. Whey from mature milk showed only the first peak. Purified bLPO and MPO showed chromatographic behaviors that were similar to the first and second peaks, respectively. The dapsone-sensitive peroxidase from mature milk was further purified (952-fold from whey) by hydrophobic interaction chromatography. This preparation showed two bands with molecular masses of 80 and 90 kDa by polyacrylamide gel electrophoresis and immunoblotting using an antibody against bLPO. After deglycosylation, two distinct proteins with lower molecular weights were observed. Amino acid sequencing indicated that both of these proteins are LPO. These results provide evidence that LPO is present in mature human milk and that it is responsible for most of the peroxidase activity in mature milk.

Clinical and pathologic evaluation of chronic Bartonella henselae or Bartonella clarridgeiae infection in cats

Human Bartonella infections result in diverse medical presentations, whereas many cats appear to tolerate chronic bacteremia without obvious clinical abnormalities. Eighteen specific-pathogen-free cats were inoculated with Bartonella henselae- and/or Bartonella clarridgeiae-infected cat blood and monitored for 454 days. Relapsing bacteremia did not correlate with changes in protein profiles or differences in antigenic protein recognition. Intradermal skin testing did not induce a delayed type hypersensitivity reaction to cat scratch disease skin test antigen. Thirteen cats were euthanatized at the end of the study. Despite persistent infection, clinical signs were minimal and gross necropsy results were unremarkable. Histopathology revealed peripheral lymph node hyperplasia (in all of the 13 cats), splenic follicular hyperplasia (in 9 cats), lymphocytic cholangitis/pericholangitis (in 9 cats), lymphocytic hepatitis (in 6 cats), lymphoplasmacytic myocarditis (in 8 cats), and interstitial lymphocytic nephritis (in 4 cats). Structures suggestive of Bartonella were visualized in some Warthin-Starry stained sections, and Bartonella DNA was amplified from the lymph node (from 6 of the 13 cats), liver (from 11 cats) heart (from 8 cats), kidney (from 9 cats), lung (from 2 cats), and brain (from 9 cats). This study indicates that B. henselae or B. clarridgeiae can induce chronic infection following blood transfusion in specific-pathogen-free cats and that Bartonella DNA can be detected in blood, brain, lymph node, myocardium, liver, and kidney tissues of both blood culture-positive cats and blood culture-negative cats. Detection of histologic changes in these cats supports a potential etiologic role for Bartonella species in several idiopathic disease processes in cats.

The effects of 2-bromopropane on viability and testosterone production ability of rat Leydig cells in primary culture

Epidemiological surveys and animal experiments have shown that 2-bromopropane induces oligozoospermia in exposed workers and inhibits spermatogensis in laboratory animals. However, the mechanism by which 2-bromopropane exerts its effects is unknown. To this end, we examined the formation of testosterone by the Leydig cells and their survival of these cells in the presence of different concentrations of 2-bromopropane in vitro. Leydig cells were isolated following vascular perfusion, enzymatic dissociation and Percoll gradient centrifugation techniques. The cells were cultured in culture dishes. After 8 h, different cultures were exposed to 2-bromopropane at concentrations of 0.01 mmol/L, 0.10 mmol/L and 1.00 mmol/L. In order to stimulate Leydig cells to secrete testosterone, human chorionic gonadotropin (hCG) was also added. Cell viability was determined using the trypan blue dye exclusion test and cell numbers were counted by hemocytometer. Testosterone secretion was detected by radioimmunoassay. The cell viability decreased after exposure to 2-bromopropane in a dose-dependent way, but no morphological change was observed. The cell number decreased in the 2-bromopropane-treated cultures. The secretion of testosterone did not manifest defectable changes in the culture treated with 0.10 mmol/L and 0.01 mmol/L of 2-bromopropane; however, it decreased significantly (P < 0.02) in the presence of 1.00 mmol/L. Therefore, our results strongly suggest that 2-bromopropane may exert its cytotoxic effects on Leydig cells in vitro. We speculate that the decrease in the numbers of Leydig cells caused by 2-bromopropane was mediated by a feedback mechanism resulting from a lower testosterone concentration.

The mechanism of in vivo bacteriostasis of bovine lactoferrin

Recently we have reported that orally administered bovine Lf(bLf) exerts bacteriostatic effects against bacterial overgrowth in the intestine of specific-pathogen-free (SPF) mice fed milk. In this animal model, the in vivo bacteriostatic effect of bLf against the proliferation of intestinal Enterobacteriaceae, the bacteria most sensitive to bLf, was independent of the iron-chelating ability of bLf. In addition various proteolytic hydrolysates of bLf (with differing antibacterial activities in vitro) showed the same bacteriostatic effect as undigested bLf. These results suggest that the mechanism of in vivo bacteriostasis of Lf differs from the in vitro mechanism reported. In SPF mice fed milk differing in concentrations of lactose, glucose and galactose, the proliferation of intestinal Enterobacteriaceae was dependent on the carbohydrate concentration in the diet. The addition of 2% bLf to the diets significantly suppressed this carbohydrate-dependent proliferation of bacteria except in the case of diets containing excess carbohydrate. In germ-free mice fed sterile milk, the addition of 2% bLf to milk resulted in a significant decrease in concentrations of lactose, glucose and galactose in the cecal contents. In an in vitro assay system using everted sacs of the small intestine of SPF mice, both bLf and its pepsin hydrolysate apparently stimulated glucose absorption. Based on these findings, we propose that the in vivo mechanism of action of ingested bLf involves the stimulation of carbohydrate absorption resulting in a bacteriostatic effect against Enterobacteriaceae in the intestine of mice fed milk.

The influence of controlled occlusal overload on peri-implant tissue: a histologic study in monkeys

This study examined the influence of controlled occlusal overload on an implant. An experiment was conducted on five crab-eating monkeys (Macaca fascicularis) in which overload with no inflammation in the peri-implant tissues was modeled. Two osseointegrated implants were placed into each monkey. After 3 months of osseointegration, superstructures that were excessive by about 100 microns were mounted on the implants, and a traumatic occlusal force was experimentally delivered to its implant from the lingual to the buccal side. This procedure was performed under conditions of good oral hygiene. The monkeys received an excessive occlusal force for 1 to 4 weeks and were then immediately sacrificed. The results showed that the implants remained firmly integrated with bone, and all of the subjects that received excessive occlusal force for 1 to 4 weeks showed an absence of gross bone loss. These results suggest that conditions of occlusal force created by excessively high implant-supported superstructures may not destroy the peri-implant tissues.

Antibacterial activity of bovine lactoferrin and its peptides against enterohaemorrhagic Escherichia coli O157:H7

The antimicrobial activities of bovine lactoferrin (bLF), its pepsin hydrolysate (bLFH) and the active peptide lactoferricin B (LFcinB) against four clinical isolates of enterohaemorrhagic Escherichia coli O157:H7 were studied. The MICs against these isolates were 3 mg ml-1 for bLF, 0.1-0.2 mg ml-1 for bLFH and 8-10 micrograms ml-1 for LFcinB in 1% Bactopeptone broth. LFcinB killed these bacteria within 3 h at concentrations above 10 micrograms ml-1. Transmission electron microscopy findings suggested that LFcinB acts on the bacterial surface and affects cytoplasmic contents. LFcinB was shown to influence the levels of verotoxins in the culture supernatant fluid of an E. coli O157:H7 strain. These results demonstrate that E. coli O157:H7 strains are susceptible to the antimicrobial effects of bLF and its peptides.

Humoral immune and clinical responses to food antigens following acute diarrhoea in children

OBJECTIVE

To investigate the effect of acute watery diarrhoea in children upon humoral immune responses to food antigens and the subsequent development of food allergy.

METHODOLOGY

Serum antibodies to cows' milk, beta-lactoglobulin, alpha-lactalbumin, bovine serum albumin and ovalbumin were measured in 30 children with acute diarrhoea in the acute phase and 1 month after recovery. The children were followed for 1 year to assess the development of food allergy.

RESULTS

IgG antibeta-lactoglobulin titres for the study group increased 1 month after recovery compared to the titres during the acute phase (P = 0.02). Antibody concentration for the other antigens studied did not rise. Four children developed positive IgE antibodies to one or more of the allergens after the diarrhoeal episode, although the titres were very low. None showed evidence of allergy to cows' milk or egg during the year-long follow-up.

CONCLUSIONS

Acute diarrhoea in children resulted in increased production of IgG antibody to beta-lactoglobulin and had a priming effect for development of positive IgE antibody to cows' milk. Clinical food allergy was not observed in any of the children during the year-long follow-up.

Autonomic differences between athletes and nonathletes: spectral analysis approach

The purpose of this study was to assess the adaptive effects of endurance training on autonomic function in athletes with spectral analysis of cardiovascular variability signals. Continuous ECG, arterial blood pressure (ABP), and respiratory signals were recorded from 15 athletes (VO2max > 55 mL.min-1.kg-1) and 15 nonathletes (VO2max < 45 mL.min-1.kg-1) during 10 min at sitting position. Autonomic function was assessed by low frequency power (LF power: 0.06-0.14 Hz) and high frequency power (HF power: the region of the respiratory frequency based on respiratory spectrum) obtained from the autospectra of RR interval, systolic arterial pressure (SAP), and diastolic arterial pressure (DAP) variability signals. The spontaneous baroreflex sensitivity was evaluated by the moduli, BRSLF and BRSHF, of the transfer function between RR interval and SAP variability in LF and HF bands. The resting HR in athletes was significantly lower than that in nonathletes. The HF power, an index of parasympathetic activity, in RR interval spectra were significantly higher in athletes than in nonathletes. Meanwhile, the LF power (an indicator of sympathetic activities contributing to RR interval and of ABP variabilities) showed no significant difference between both groups, although that of athletes was slightly less than that of nonathletes. Also, BRSLF and BRSHF were not significantly different between athletes and nonathletes. These results indicate that endurance training results in the enhanced vagal activities in athletes, which may contribute in part to the resting bradycardia.

[Pleural-origin malignant lymphoma in an elderly patient with chronic empyema and infection with the Epstein-Barr virus]

A 73-year-old woman with a long-standing history of right-sided chronic empyema complained of lumbago. An artificial pneumothorax had been induced to treat pulmonary tuberculosis about 40 years previously. The year after she began to complain of lumbago, a tumor mass over the right anterior chest wall had grown rapidly. Pathologic examination revealed that it was a malignant lymphoma (Non-Hodgkin's lymphoma, diffuse large cell, B cell type). Chemotherapy with cyclophosphamide, adriamycin, vincristine, and prednisolone, and then radiation therapy were given. The patient responded very well. The tumor mass on the surface of the chest wall disappeared completely. She was alive and well and there was no evidence of recurrence at the seven-month follow-up examination. Analysis with the polymerase chain reaction showed that the tumor contained DNA of the Epstein-Barr virus. The chronic empyema and local infection with the Epstein-Barr virus might have been a factor in the development of the malignant lymphoma.

Production and Purification of Remazol Brilliant Blue R Decolorizing Peroxidase from the Culture Filtrate of Pleurotus ostreatus

An extracellular H(inf2)O(inf2)-requiring Remazol brilliant blue R (RBBR) decolorizing enzymatic activity was found in the culture medium of Pleurotus ostreatus. The enzymatic activity was maximally obtained in idiophase, and the optimum C/N ratio was 24. High C/N ratios repressed the enzymatic activity, and addition of veratryl alcohol had no effect on the production of enzyme. The enzyme was purified by ammonium sulfate fractionation, Sephacryl S-200 HR chromatography, DEAE Sepharose CL-6B chromatography, and Mono Q chromatography. The purification of RBBR decolorizing peroxidase, as judged by the final specific activity of 6.00 U/mg, was 54.5-fold, with a yield of 9.9%. The molecular mass of the native enzyme determined by gel permeation chromatography was found to be about 73 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the enzyme was a monomer with a molecular mass of 71 kDa. The enzyme was optimally active at pH 3.0 to 3.5 and at 25(deg)C. Under standard assay conditions, the apparent K(infm) values of the enzyme toward RBBR and H(inf2)O(inf2) were 10.99 and 32.97 (mu)M, respectively. The enzyme had affinity toward various phenolic compounds and artificial dyes, and it was inhibited by Na(inf2)S(inf2)O(inf5), potassium cyanide, NaN(inf3), and cysteine. The absorption spectrum of the enzyme exhibited maxima at 407, 510, and 640 nm. The addition of H(inf2)O(inf2) to the enzyme resulted in an absorbance decrease at 407 and 510 nm.

[An elderly patient with Ph1-positive chronic myelomonocytic leukemia]

An 80-year-old man with leukocytosis was admitted to our hospital on February 20, 1995. There were no blasts in the peripheral blood, but leukocytosis, associated with marked monocytosis, anemia, and thrombocytopenia was observed. The bone marrow was hyperplastic and there was a slight decrease in megakaryocytes. The myelogram showed 5.6% blasts + promyelocytes, and there was no basophilia. Mild dysplasia of third-line cells was observed. Chromosome analysis yielded 47, XY, +8, t (9;22) (q34;q11), and the Philadelphia (Ph1) chromosome and trisomy 8 were detected. Fluorescence in-situ hybridization revealed a large ber. Because the French-American-British (FAB) cooperative group diagnostic criteria for chronic myelomonocytic leukemia (CMMoL) were fulfilled and the Ph1 chromosome was detected, a diagnosis of Ph1-positive CMMoL was made. Hydroxyurea was given for cytoreduction and the patient has been followed with no evidence of acute transformation for about one year. CMMoL is classified as a myelodysplastic syndrome. However, it is rare to find the Ph1 chromosome in patients with these syndromes, and there have been very few reports of its detection in CMMoL. CMMoL may not be a single disease entity, and it may be useful to investigate more cases like the present one, to reassess this disease.

Glycans of bovine lactoferrin function as receptors for the type 1 fimbrial lectin of Escherichia coli

Bovine lactoferrin strongly inhibited the hemagglutination activity of type 1 fimbriated Escherichia coli. In addition, it agglutinated these bacteria. The agglutination reaction was specifically inhibited by glycopeptides derived from bovine lactoferrin or alpha-methyl-D-mannoside. These observations indicate that the glycans of bovine lactoferrin can serve as receptors for type 1 fimbrial lectin.