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Biomedical subjects

H B Lin

Publications and source records attributed to H B Lin.

28 records · Page 2Linked to original sources
PubMed1990

Regulation of renin release and renal hemodynamics during acute and chronic verapamil administration.

The effects of short- and long-term administration of the calcium-entry blocker verapamil on regulation of renal hemodynamics and renin release were analyzed in anesthetized dogs at controlled levels of renal perfusion pressure between 110 and 60 mmHg. The following three groups of dogs were studied: a control group, an acutely treated verapamil group (initial dose of 150 micrograms/kg followed by 4 micrograms.kg-1.min-1), and a chronically treated verapamil group (240 mg per os twice each day). At 110 mmHg the renal blood flow (RBF) in the acutely and chronically treated groups was 53% greater than (P less than 0.03) and 79% greater than (P less than 0.01) that of the control group. Glomerular filtration rate (GFR) in the acutely and chronically treated groups was 64 and 92%, respectively, greater than (P less than 0.01 for both) that of the control group. Autoregulation of RBF and GFR was extremely effective in the control group, whereas it was severely impaired by acute and long-term treatment with verapamil. Renin release at 110 mmHg in the control and the acutely treated groups were similar, 3.36 +/- 0.96 and 4.46 +/- 0.64 U.min-1.g-1, respectively, although in the chronically treated group the rate of release was 8.89 +/- 2.60 U.min-1.g-1 (P less than 0.03). As perfusion pressure was reduced, the rate of release from the acutely treated group rose to higher levels than that of the control group; at 70 mmHg release from the acutely treated group was 88% greater than that of the control group (P less than 0.01). Verapamil profoundly alters regulation of renal hemodynamics and renin release and the effect is prominent during both short- and long-term administration.

Animals↗
PubMed1989

Acoustic properties and perception of stop consonant release transients.

This study focuses on the initial component of the stop consonant release burst, the release transient. In theory, the transient, because of its impulselike source, should contain much information about the vocal tract configuration at release, but it is usually weak in intensity and difficult to isolate from the accompanying frication in natural speech. For this investigation, a human talker produced isolated release transients of /b,d,g/ in nine vocalic contexts by whispering these syllables very quietly. He also produced the corresponding CV syllables with regular phonation for comparison. Spectral analyses showed the isolated transients to have a clearly defined formant structure, which was not seen in natural release bursts, whose spectra were dominated by the frication noise. The formant frequencies varied systematically with both consonant place of articulation and vocalic context. Perceptual experiments showed that listeners can identify both consonants and vowels from isolated transients, though not very accurately. Knowing one of the two segments in advance did not help, but when the transients were followed by a compatible synthetic, steady-state vowel, consonant identification improved somewhat. On the whole, isolated transients, despite their clear formant structure, provided only partial information for consonant identification, but no less so, it seems, than excerpted natural release bursts. The information conveyed by artificially isolated transients and by natural (frication-dominated) release bursts appears to be perceptually equivalent.

Humans↗
PubMed1989

Effects of preceding context on discrimination of voice onset times.

When discriminating pairs of speech stimuli from an acoustic voice onset time (VOT) continuum (for example, one ranging from /ba/ to /pa/), English-speaking subjects show a characteristic performance peak in the region of the phonemic category boundary. We demonstrate that this "category boundary effect" is reduced or eliminated when the stimuli are preceded by /s/. This suppression does not seem to be due to the absence of a phonological voicing contrast for stop consonants following /s/, since it is also obtained when the /s/ terminates a preceding word and (to a lesser extent) when broadband noise is substituted for the fricative noise. The suppression is stronger, however, when the noise has the acoustic properties of a syllable-initial /s/, all else being equal. We hypothesize that these properties make the noise cohere with the following speech signal, which makes it difficult for listeners to focus on the VOT differences to be discriminated.

Adult↗
PubMed1988

Verapamil alters the relationship between renal perfusion pressure and glomerular filtration rate and renin release: the mechanism of the antihypertensive effect.

The renal hemodynamic and renin release responses to verapamil were analyzed in order to determine if the antihypertensive action of the calcium entry blocker could be due to its renal effects. Hemodynamic and renin release measurements were compared in a control group of anesthetized rabbits (N = 9) and in a group of rabbits given verapamil (N = 10) (200 micrograms/kg i.v. initially, 4 micrograms/kg/min thereafter) starting 30 min before data collection. Measurements were made over a range of controlled renal perfusion pressure from 100 to 40 mm Hg. The renal blood flow (RBF) at 100 mm Hg of the verapamil-treated group was 18% greater than (p less than 0.02) that of the control group, while the glomerular filtration rate (GFR) was 51% greater than (p less than 0.001) that of the control group. RBF and GFR autoregulation was highly effective in the control group down to 80 mm Hg, but both variables were poorly regulated in the verapamil group. The filtration fraction of the treated group was 36.9 +/- 1.5% versus 28.5 +/- 1.6% in the control group (p less than 0.003) at 100 mm Hg, and the filtration fraction of the treated group remained significantly greater down to 40 mm Hg. Renin release rates of the two groups were similar at the 100 mm Hg pressure level, but the increase in release due to the progressive reduction in perfusion pressure was significantly greater in the treated group than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Impaired control of renal hemodynamics and renin release during hyperkalemia in rabbits.

We analyzed the changes in control of renal hemodynamics and renin release resulting from hyperkalemia in the rabbit. Plasma potassium activity was maintained at a controlled elevated level by intravenous infusion of KCl. The potassium activity of the control group (n = 23) averaged 3.20 +/- 0.06 meq/l and that of the hyperkalemic group (n = 13) averaged 5.80 +/- 0.13 meq/l. Renal blood flow (RBF), glomerular filtration rate (GFR), and renin release were measured over a range of renal perfusion pressures achieved by constriction of the suprarenal aorta. The control group's RBF and GFR exhibited excellent autoregulatory capability from 100 to 80 mmHg. However, significant impairment of autoregulation was apparent in the hyperkalemic group. At 100 mmHg, RBF and GFR in the hyperkalemic group averaged 33 and 34% greater, respectively, than those of the control group (P less than 0.005); both variables in the hyperkalemic group were greater than the values of the control group over the autoregulatory range (100-80 mmHg). The renin release values for the two groups were not different at the 100-mmHg pressure level, although renin release of the hyperkalemic group increased to higher levels than those of the control group as perfusion pressure was reduced. At the 70- and 60-mmHg levels renin release from the hyperkalemic group averaged approximately 300% greater than that of the control group (P less than 0.05). However, when expressed as percentage change, the stimulatory effect of hyperkalemia was not apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The antihypertensive mechanism of verapamil. Alteration of glomerular filtration rate regulation.

The renal hemodynamic and renin release responses to verapamil were analyzed to determine if the antihypertensive action of the calcium entry blocker could be due to its renal effects. Hemodynamic and renin release measurements were compared in a control group of nine anesthetized rabbits and in a group of 10 rabbits given verapamil (200 micrograms/kg i.v. initially, 4 micrograms/kg/min thereafter), starting 30 minutes before data collection. Measurements were made over a range of controlled renal perfusion pressure from 100 to 40 mm Hg. The renal blood flow at 100 mm Hg of the verapamil-treated group was 18% greater (p less than 0.02) than that of the control group, while the glomerular filtration rate was 51% greater (p less than 0.001) than that of the control group. Renal blood flow and glomerular filtration rate autoregulation were highly effective in the control group down to 80 mm Hg, but both variables were poorly regulated in the verapamil-treated group. The filtration fraction of the treated group was 36.9 +/- 1.5% versus 28.5 +/- 1.6% in the control group (p less than 0.003) at 100 mm Hg, and the filtration fraction of the treated group remained significantly greater down to 40 mm Hg. Renin release rates of the two groups were similar at the 100 mm Hg pressure level, but the increase in release due to the progressive reduction in perfusion pressure was significantly greater in the treated group than in the control group. At the 80 mm Hg pressure level, the mean release rate for the treated group was more than three times greater (p less than 0.05) than that of the control group. These findings demonstrate that verapamil is an effective renal vasodilator and that the effect is proportionally greater on the preglomerular than on the postglomerular resistance. This action could be the basis for its antihypertensive efficacy.

Animals↗
PubMedDate not supplied

In vivo evaluation of a new type I collagen hemostatic plug for high-risk, large-core biopsies.

PURPOSE: To evaluate in a swine model the hemostatic properties of a new, expansile type I collagen plug for use in high-risk renal biopsies. MATERIALS AND METHODS: Highly purified bovine type I collagen was formed into porous cylindrical plugs and compressed radially to fit into a 5-F delivery system. On hydration these collagen plugs demonstrated radial expansion with approximately 1,600% volumetric expansion ratio. Direct exposure of both kidneys was performed in a 25-kg swine, and a bolus of 3,000 U of heparin was administered to create a coagulopathic state. A 14-gauge Temno coaxial biopsy gun was utilized in performing nine pairs of renal biopsies. The first biopsy of each biopsy pair represented the control biopsy (without collagen plug placement), whereas the second biopsy of each pair represented the plugged biopsy. The presence and duration of hemorrhage from each biopsy site was monitored visually. RESULTS: The biopsy sites without collagen plug showed immediate hemorrhage in nine of nine cases (100%), and in two of nine cases (22%) pulsatile bleeding was noted. With the use of the collagen plug, seven of nine (78%) sites showed immediate hemorrhage, but in no case was pulsatile bleeding noted. Mean bleeding duration was 156 seconds for the control biopsies versus 73 seconds for the biopsy sites plugged with collagen (P = .03, Mann-Whitney rank sum test). Bleeding duration was less than 1 minute in only one of nine (11%) control biopsies compared to six of nine (67%) collagen plug biopsies. CONCLUSIONS: A recently developed, expansile collagen hemostatic plug significantly decreases the duration of hemorrhage at renal biopsy sites in an anticoagulated swine model.

Animals↗
PubMedDate not supplied

Cues to the perception of Taiwanese tones.

A labeling test with synthetic speech stimuli was carried out to determine to what extent the two dimensions of fundamental frequency (F0), height and movement, and syllable duration provide cues to tonal distinctions in Taiwanese. The data show that the high level vs. mid level tones and the high falling vs. mid falling tones can be reliably distinguished by F0 height alone, whereas the distinction between tones with dissimilar contours, such as the high falling and low rising tones, is predominantly cued by F0 movement. However, the other dimension of F0 may collaborate with the dominant one in cueing a tonal contrast, depending on the extent to which the two tones differ along that dimension. Syllable duration has a small additional effect on the perception of the distinction between falling and nonfalling tones. These results are consistent with previous findings in tone languages other than Taiwanese in that they suggest that tones are mainly cued by F0. While the primacy of F0 dimensions as cues to tonal contrasts depends on the contrast to be distinguished, the present findings show that tones which nominally differ only in register (e.g., high falling vs. mid falling) may exhibit perceptually relevant contour differences, and vice versa.

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