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Biomedical subjects

V Mann

Publications and source records attributed to V Mann.

At least 19 recordsLinked to original sources
PubMed1996

Lexical familiarity and English-language experience affect Japanese adults' perception of / / and /l/.

This study assessed the influence of subjective lexical familiarity and English-language experience on Japanese adults' accuracy in identifying singleton word-initial tokens of English [symbol: see text] and /l/. The inexperienced Japanese (IJ) subjects had lived in the U.S. for 2 years, whereas the experienced Japanese (EJ) subjects had lived there for 21 years, on average. The native Japanese subjects correctly identified English [symbol: see text] and /l/ tokens less often than did a group of native English (NE) subjects, but they did not differ from the NE subjects in identifying the control consonants /w/ and /d/. The NE subjects, who were at ceiling, showed no effect of subjective lexical familiarity. However, the EJ and IJ subjects correctly identified [symbol: see text] and /l/ tokens more often in words that were more familiar than their minimal pairs than in words that were less familiar than their minimal pairs. The EJ subjects identified liquids more often than did the IJ subjects, but usually less often than the NE subjects. However, the EJ subjects managed to identify [symbol: see text] tokens at rates comparable to the NE subjects' rates in words that wer matched in subjective familiarity to their minimal pair (experiment 1), and when identifying [symbol: see text] tokens that had been edited out of their original word or nonword context (experiment 2).

Humans↗
PubMed1994

Cloning and characterization of the gene for phytoene desaturase (Pds) from tomato (Lycopersicon esculentum).

The gene Pds encodes phytoene desaturase, a key enzyme in carotenoid biosynthesis that converts phytoene to zeta-carotene. We have cloned and analyzed the genomic DNA sequence of Pds from tomato. In tomato Pds is comprised of 15 exons that, together with the introns occupy over 8 kb. A putative promoter sequence has been identified by comparison with the cDNA sequence of Pds. A consensus nucleotide sequence around intron splicing sites in tomato genes was determined by compiling data on 137 introns in 34 genes. This consensus sequence generally agrees with the consensus sequence of other higher plants with only minor differences that are unique to tomato.

Amino Acid Sequence↗
PubMed1994

Use of vocalic cues to consonant voicing and native language background: the influence of experimental design.

For native speakers of English and several other languages, preceding vocalic duration and F1 offset frequency are two of the cues that convey the stop consonant voicing distinction in word-final position. For speakers learning English as a second language, there are indications that use of vocalic duration, but not F1 offset frequency, may be hindered by a lack of experience with phonemic (i.e., lexical) vowel length (the "phonemic vowel length account": Crowther & Mann, 1992). In this study, native speakers of Arabic, a language that includes a phonemic vowel length distinction, were tested for their use of vocalic duration and F1 offset in production and perception of the English consonant-vowel-consonant forms pod and pot. The phonemic vowel length hypothesis predicts that Arabic speakers should use vocalic duration extensively in production and perception. On the contrary, Experiment 1 revealed that, consistent with Flege and Port's (1981) findings, they produced only slightly (but significantly) longer vocalic segments in their pod tokens. It further indicated that their productions showed a significant variation in F1 offset as a function of final stop voicing. Perceptual sensitivity to vocalic duration and F1 offset as voicing cues was tested in two experiments. In Experiment 2, we employed a factorial combination of these two cues and a finely spaced vocalic duration continuum. Arabic speakers did not appear to be very sensitive to vocalic duration, but they were about as sensitive as native English speakers to F1 offset frequency. In Experiment 3, we employed a one-dimensional continuum of more widely spaced stimuli that varied only vocalic duration. Arabic speakers showed native-English-like sensitivity to vocalic duration. An explanation based on the perceptual anchor theory of context coding (Braida et al., 1984; Macmillan, 1987; Macmillan, Braida, & Goldberg, 1987) and phoneme perception theory (Schouten & Van Hessen, 1992) is offered to reconcile the apparently contradictory perceptual findings. The explanation does not attribute native-English-like voicing perception to the Arabic subjects. The findings in this study call for a modification of the phonemic vowel length hypothesis.

Adolescent↗
PubMed1992

Native language factors affecting use of vocalic cues to final consonant voicing in English.

Preceding vocalic information can cue final consonant voicing for native English speakers. This study examines subjects' use of two vocalic cues, vocalic duration, and F1 offset frequency, as a function of two native language factors, experience with final stop consonants, and experience with phonemic vowel length. Native speakers of English are compared to native speakers of Japanese and Mandarin Chinese who are learning English as a second language. Experiment 1 measured the F1 offset frequency and vocalic duration in productions of "pod" and "pot." Experiment 2 assessed identification of natural tokens of "pod" and "pot" with and without closure segments and bursts. Experiment 3 assessed categorization of synthetic "pod"-"pot" stimuli that systematically manipulated vocalic duration and F1 offset frequency. Native speakers of English showed the strongest implementation of and sensitivity to vocalic duration, Mandarin speakers showed significantly weaker effects, and Japanese speakers fell in between. Group-related differences in use of F1 offset frequency were smaller, and much clearer in the case of production than perception. It is hypothesized that a lack of experience with final consonants penalizes use of vocalic cues among the Japanese and Mandarin subjects, in general. The advantage of the Japanese subjects for use of vocalic duration further suggests a facilitation effect of experience with phonemic vowel length.

Adolescent↗
PubMed1991

PCR-detected genital papillomavirus infection: prevalence and association with risk factors for cervical cancer.

In an investigation conducted in student health clinic patients, the polymerase chain reaction was used to detect human papillomavirus (HPV) DNA, thereby allowing measurement of the prevalence of HPV infection and study of the association between HPV infection and risk factors for cervical cancer. Of 159 women eligible to participate, 105 (66%) provided a specimen of cervical cells for HPV typing, and also answered an interviewer-administered questionnaire which sought information on risk factors for cervical cancer. Nucleic acid extracted from cervical cells was screened with primers for HPV types 6, 11, 16, 18, 33 and with an HPV Consensus primer. Overall, the prevalence of HPV infection was 18.1%, while for HPV-6/11 it was 2.9% and for HPV-16/18 it was 10.5%. There were statistically significant increases in risk of HPV infection with a history of ever having smoked cigarettes (overall, and for HPV-16 alone) and with a history of usually having sexual intercourse during menstrual periods (overall, but not for HPV-16), and these associations were independent of the effects of age at first sexual intercourse and number of sexual partners. The latter 2 variables, as well as the total number of occasions of sexual intercourse, a history of anal intercourse, and a history of ever having used oral contraceptives, were not associated with statistically significant alterations in risk of HPV infection.

Adult↗
PubMed1991

Herpes simplex virus type 2: a possible interaction with human papillomavirus types 16/18 in the development of invasive cervical cancer.

A case-control study of 766 histologically confirmed incident cases of invasive cervical cancer and 1,532 hospital and community controls was conducted in Latin America to evaluate the etiologic role of herpes simplex virus type 2 (HSV-2) and to examine whether HSV-2 interacts with other risk factors. In addition to a personal interview, all subjects were asked to donate blood samples and cervical swabs for assessment of exposure to HSV-2 and human papillomaviruses (HPVs) respectively. Ninety-eight percent of cases and 91% of controls agreed to the interview and blood collection. Women testing positive for HSV-2 antibodies were found to have a 60% increased risk of cervical cancer compared with seronegative women (95% CI = 1.3, 1.9). Control for education, sexual and reproductive behavior, prior Pap-smear screening, smoking, oral contraceptive use, HPV-6/11 DNA, or HPV-16/18 DNA detection did not materially affect this estimate. No effect modification of HSV-2 by age, HPV-6/11 DNA, pregnancies, oral contraceptive use or cigarette smoking was observed. However, a significant interaction was detected between HSV-2 and HPV-16/18. Compared with women testing negative to both virus types, those positive for HSV-2 alone had a RR of 1.2 (95% CI = 0.9, 1.6), those positive for HPV-16/18 DNA alone had a RR of 4.3 (95% CI = 3.0, 6.0), and those positive for both viruses had a RR of 8.8 (95% CI = 5.9, 13.0). These findings corroborate recent laboratory evidence of a possible biological interaction between HSV-2 and HPV-16/18 in the development of cervical cancer. Further confirmatory studies are needed, given concerns with potential misclassification of exposure by the laboratory assays utilized.

Adult↗
PubMed1991

Human papillomavirus types 16 and 33, herpes simplex virus type 2 and other risk factors for cervical cancer in Sichuan Province, China.

Cancer of the cervix is relatively common in China, but has been investigated epidemiologically in only a few studies. In the hospital-based case-control study reported here, we investigated the role of various lifestyle and dietary factors, as well as infection with human papillomavirus (HPV) types 16 and 33 and herpes simplex virus type 2 in the aetiology of invasive cervical cancer. The study was conducted in Sichuan province, and involved 101 cases with histologically-confirmed cervical cancer recruited from the gynaecological oncology clinic of the West China University Hospital, and 146 controls recruited from patients attending the gynaecology clinic of the same hospital. Risk of cervical cancer was greatly increased in association with infection with HPV 16/33, the adjusted odds ratio for those with evidence of infection being 32.9 (95% CI 7.7-141.1). In contrast, infection with HSV 2 was not associated with a significantly altered risk of cervical cancer. Indices of sexual history and of dietary habits also showed no association with risk of cervical cancer, while good personal and genital hygiene were associated with markedly reduced risk. Although the results of this study are consistent with a causal role for HPV in the aetiology of cervical cancer, bias or increased viral expression following malignant transformation cannot be excluded as explanations for the strong positive association.

Case-Control Studies↗
PubMed1991

The cytochrome oxidase II gene in mitochondria of the sugar-beet Beta vulgaris L.

We have cloned and analyzed the sugar-beet mitochondrial gene for cytochrome oxidase subunit II (coxII). The sugar-beet and its deduced amino acid sequence were compared to its homologous coxII gene sequences from both monocot and dicot plants. It was found to be highly conserved (89-95%) compared to homologue in other plant species. The 780 bp coding sequence of the sugar beet coxII gene is interrupted at position 383 by a 1463 bp intron. This intron contains an additional 107 bp sequence that is not found in any of the plant coxII genes studied thus far. The structure of the intron suggests that a large intron existed in an ancestral coxII gene before monocots and dicots diverged in evolution. Three CGG codons in the sugar-beet coxII coding sequence align with conserved tryptophan residues in the homologous gene of other species, suggesting that RNA editing takes place also in sugar-beet mitochondria. In 13 out of 24 codons of coxII mRNA that were found to be edited in four other plants, the sugar-beet gene already utilizes the edited codons. This phenomenon may indicate that the mitochondrial genome in sugar-beet is phylogenetically more archaic relative to these plants. An additional sequence of 279 bp that is identical to the first exon of coxII was identified in the mtDNA of the sugar-beet. This 'pseudo-gene' is transcribed and its existence in the mitochondrial genome is unexplained.

Amino Acid Sequence↗
PubMed1991

Perceptual order and the effect of vocalic context of fricative perception.

This three-part study demonstrates that perceptual order can influence the integration of acoustic speech cues. In Experiment 1, the subjects labeled the [s] and [sh] in natural FV and VF syllables in which the frication was replaced with synthetic stimuli. Responses to these "hybrid" stimuli were influenced by cues in the vocalic segment as well as by the synthetic frication. However, the influence of the preceding vocalic cues was considerably weaker than was that of the following vocalic cues. Experiment 2 examined the acoustic bases for this asymmetry and consisted of analyses revealing that FV and VF syllables are similar in terms of the acoustic structures thought to underlie the vocalic context effects. Experiment 3 examined the perceptual bases for the asymmetry. A subset of the hybrid FV and VF stimuli were presented in reverse, such that the acoustic and perceptual bases for the asymmetry were pitted against each other in the listening task. The perceptual bases (i.e., the perceived order of the frication and vocalic cues) proved to be the determining factor. Current auditory processing models, such as backward recognition masking, preperceptual auditory storage, or models based on linguistic factors, do not adequately account for the observed asymmetries.

Attention↗
PubMed1990

Masking and stimulus intensity effects on duplex perception: a confirmation of the dissociation between speech and nonspeech modes.

Using the phenomenon of duplex perception, previous researchers have shown that certain manipulations affect the perception of formant transitions as speech but not their perception as nonspeech "chirps," a dissociation that is consistent with the hypothesized distinction between speech and nonspeech modes of perception [Liberman et al., Percept. Psychophys. 30, 133-143 (1981); Mann and Liberman, Cognition 14, 211-235 (1983)]. The present study supports this interpretation of duplex perception by showing the existence of a "double dissociation" between the speech and chirp percepts. Five experiments compared the effects of stimulus onset asynchrony, backward masking, and transition intensity on the two sides of duplex percepts. It was found that certain manipulations penalize the chirp side but not the speech side, whereas other manipulations had the opposite effect of penalizing the speech side but not the chirp side. In addition, although effects on the speech side of duplex percepts have appeared to be much the same as in the case of normal (electronically fused) speech stimuli, the present study discovered that manipulations that impaired the chirp side of duplex percepts had considerably less effect on the perception of isolated chirps. Thus it would seem that duplex perception makes chirp perception more vulnerable to the effects of stimulus degradation. Several explanations of the data are discussed, among them, the view that speech perception may take precedence over other forms of auditory perception [Mattingly and Liberman, in Signals and Sense: Local and Global Order in Perceptual Maps, edited by G.M. Edelman, W.E. Gall, and W.M. Cowan (Wiley, New York, in press); Whalen and Liberman, Science 237, 169-171 (1987)].

Adult↗
PubMed1989

Myelin membrane structure and composition correlated: a phylogenetic study.

We have correlated myelin membrane structure with biochemical composition in the CNS and PNS of a phylogenetic series of animals, including elasmobranchs, teleosts, amphibians, and mammals. X-ray diffraction patterns were recorded from freshly dissected, unfixed tissue and used to determine the thicknesses of the liquid bilayer and the widths of the spaces between membranes at their cytoplasmic and extracellular appositions. The lipid and protein compositions of myelinated tissue from selected animals were determined by TLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis/immunoblotting, respectively. We found that (1) there were considerable differences in lipid (particularly glycolipid) composition, but no apparent phylogenetic trends; (2) the lipid composition did not seem to affect either the bilayer thickness, which was relatively constant, or the membrane separation; (3) the CNS of elasmobranch and teleost and the PNS of all four classes contained polypeptides that were recognized by antibodies against myelin P0 glycoprotein; (4) antibodies against proteolipid protein (PLP) were recognized only by amphibian and mammalian CNS; (5) wide extracellular spaces (ranging from 36 to 48 A) always correlated with the presence of P0-immunoreactive protein; (6) the narrowest extracellular spaces (approximately 31 A) were observed only in PLP-containing myelin; (7) the cytoplasmic space in PLP-containing myelin (approximately 31 A) averaged approximately 5 A less than that in P0-containing myelin; (8) even narrower cytoplasmic spaces (approximately 24 A) were measured when both P0 and 11-13-kilodalton basic protein were detected; (9) proteins immunoreactive to antibodies against myelin P2 basic protein were present in elasmobranch and teleost CNS and/or PNS, and in mammalian PNS, but not in amphibian tissues; and (10) among mammalian PNS myelins, the major difference in structure was a variation in membrane separation at the cytoplasmic apposition. These findings demonstrate which features of myelin structure have remained constant and which have become specifically altered as myelin composition changed during evolutionary development.

Animals↗
PubMed1986

Characterization of a tumorigenic murine T-lymphoid-cell line spontaneously derived from an IL-2-dependent T-cell line.

The establishment of IL-2-independent T-cell lines spontaneously derived from long-term IL-2-dependent cytotoxic T-cell lines is described. Two lines (cloned and uncloned) studied in detail have shown the following characteristics: (1) Permanent loss of IL-2 dependence. (2) Partial or complete loss of both cytotoxic activity and the IL-2 receptor. (3) Increased expression of T-cell membrane markers (Thy1.2, Lyt1.2) compared with the parental line. (4) Lower level of DNA methylation than in freshly obtained lymphoid cells. (5) Different karyotypic pattern from the parental IL-2-dependent line, with a mean number of 39-40 chromosomes and a resemblance to T leukemic lines. (6) Leukemia caused in normal syngeneic C57BL/6 mice by the uncloned line, in contrast to the cloned IL-2-independent line or the parental dependent line. Unlike established leukemic lines, however, the independent line gave rise to tumors which regressed in some mice within a few days of their appearance. These findings suggest that T-cell lines maintained with IL-2 for prolonged periods of time (greater than 3 months) can undergo transformation and, therefore, should not be utilized for immunotherapeutic purposes.

Animals↗
PubMed1985

Cell cycle-dependent regulation of eukaryotic DNA methylase level.

DNA methylase activity in the nuclei of somatic cells arrested at G0 increased markedly when the cells were subjected to a mitogenic stimulus. Treatment of mouse splenocytes with Concanavalin A resulted in about 20-fold increase in methylase activity within 20 h starting 12-15 h after Concanavalin A addition. The methylase level in rat liver was elevated approximately 3-fold at about 20-h posthepatectomy. A detailed time course of the increase in methylase activity with respect to the cell cycle revealed that the onset of this event coincided with the entry of the cells into S phase. In both systems, the extent of methylation in CpG sequences is not altered significantly even under conditions of active DNA synthesis which is induced by the mitogenic effect. These results suggest that the cell responds to the mitogenic stimulus by adjusting the DNA methylase activity to enable conservation of the methylation level in DNA.

Animals↗
PubMed1985

Cellular and viral DNA hypomethylation associated with induction of Epstein-Barr virus lytic cycle.

Epstein-Barr virus (EBV) producer and nonproducer cell lines have been treated with a combination of phorbol 12-myristate 13-acetate and n-butyrate (sodium salt). These inducers caused a massive hypomethylation of the EBV producer line P3HR-1 DNA (about 30%) at the time when DNA replication was inhibited. The viral DNA in these cells is heavily methylated as judged by digestion with Hpa II and probing with the Bam HI H fragment of EBV. However, upon induction with phorbol 12-myristate 13-acetate and n-butyrate, total hypomethylation of this viral DNA region was observed within 24 hr. This hypomethylation preceded EBV amplification, which became apparent only 32-36 hr after induction. When induction was carried out in the presence of retinoic acid, hypomethylation of cellular and viral DNA, viral DNA amplification, and production of the viral early antigen and viral capsid antigen were substantially inhibited. EBV DNA in another producer line (Jijoye nude) and in the nonproducer line Raji was hypomethylated and did not undergo further hypomethylation in response to induction. The observed hypomethylation of P3HR-1 and EBV DNA in the absence of DNA replication suggests that it is achieved by an active demethylation mechanism. This changes our perception of the DNA methylation phenomenon, since it has been generally accepted that hypomethylation of DNA takes place by a passive mechanism that involves DNA replication in the absence of methylation.

Butyrates↗
PubMed1983

Speech perception and memory coding in relation to reading ability.

Previous work has demonstrated that children who are poor readers have short-term memory deficits in tasks in which the stimuli lend themselves to phonetic coding. The aim of the present study was to explore whether the poor readers' memory deficit may have its origin in perception with the encoding of the stimuli. Three experiments were conducted with third grade good and poor readers. As in earlier experiments, the poor readers were found to perform less well on recall of random word strings and to be less affected by the phonetic characteristics (rhyming or not rhyming) of the items (Experiment 1). In addition, the poor readers produced more errors of transposition (in the nonrhyming strings) than did the good readers, a further indication of the poor readers' problems with memory for order. The subjects were tested on two auditory perception tasks, one employing words (Experiment 2) and the other nonspeech environmental sounds (Experiment 3). Each was presented under two conditions: with a favorable signal-to-noise ratio and with masking. The poor readers made significantly more errors than the good readers when listening to speech in noise, but did not differ in perception of speech without noise or in perception of nonspeech environmental sounds, whether noise-masked or not. Together, the results of the perception studies suggest that poor readers have a perceptual difficulty that is specific to speech. It is suggested that the short-term memory deficits characteristic of poor readers may stem from material-specific problems of perceptual processing.

Auditory Perception↗