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D Bock

Publications and source records attributed to D Bock.

31 records · Page 2Linked to original sources
PubMed1992

Human cerebrovascular response to oxygen and carbon dioxide as determined by internal carotid artery duplex scanning.

Alterations in arterial oxygen and carbon dioxide influence cerebrovascular resistance and therefore cerebral blood flow (CBF), but the magnitude of these CBF responses have not been well defined in normal humans. Duplex scanning (B-mode imaging and pulsed Doppler shift analysis) was used to measure internal carotid blood flow (ICBF) as an indicator of CBF in 20 normal subjects during alterations of arterial O2 and CO2. End-tidal PCO2 (PETCO2) was measured by mass spectrometry, arterial oxygen saturation by pulse oximetry, and unilateral (right) ICBF by duplex scanning. A variety of gas mixtures were administered to achieve hypoxemia (FIO2 = 0.075-0.10) and hypercapnia (FICO2 = 0.05) or the subject was asked to hyperventilate to PETCO2 = 16-24 mm Hg. The ICBF was determined five times in each of six conditions: (1) normoxia/normocapnia; (2) normoxia/hypercapnia; (3) normoxia/hypocapnia; (4) hypoxia/normocapnia; (5) hypoxia/hypercapnia; and (6) hypoxia/hypocapnia. During normoxia and normocapnia, the mean ICBF was 330 +/- 19 (SEM) mL/min. Specific CO2 reactivity was 7.4 +/- 0.7 mL/min/mmHg, which is equivalent to 2.3% +/- 0.1% of normocapnic blood flow per mm Hg change in CO2. During normocapnia, ICBF increased by 2.9 +/- 0.9 mL/min for each percentage decrease in oxygen saturation. Using an ANOVA with repeated measures to fit the responses, the following statistically significant relationship was found: ICBF (mL/min) = 333 + 6.3.(PETCO2 - 40) + 2.7 DSO2 +/- 81 where DSO2 is arterial desaturation (100 - arterial saturation). An additional "between subject" variation had a mean of 0 and a standard deviation of 82 mL/min. There was no statistically significant evidence of an interaction between O2 and CO2 response. Our data suggest that hypoxia and carbon dioxide changes will alter CBF simultaneously and additively. Duplex scanning of the internal carotid artery, which can be performed at the bedside, is sufficiently sensitive to detect changes in ICBF and internal carotid artery oxygen delivery.

Adult↗
PubMed1983

The chetotaxy of the cercaria of Opisthioglyphe locellus Kossack 1910 (Trematoda, Plagiorchiidae).

The distribution of the tegumentary papillae (chetotaxy) was studied for the cercaria of Opisthioglyphe locellus. The cercariae, which emerge from the freshwater snail Planorbarius corneus L., were treated according to the method of Ginecinskaja and Dobrovol'skij (1963). The papillae were demonstrated after the nomenclature of Richard (1971). The results were identical for cercariae from naturally infected Planorbarius corneus from a pond near Ulm (Germany) and experimentally infected, laboratory-reared snails of the same species. The papillae were distributed symmetrically with few individual variations. The association of the trematode with the subfamily Opisthioglyphinae is corroborated by the chetotaxy of the cercaria. This method also allows the distinction of the cercaria from the most related species. The fact that the excretory system of the cercaria of Opisthioglyphe locellus shows common characteristics with other cercariae of the Opisthioglyphinae (Bock 1982), just like the chetotaxy, emphasizes the taxonomic importance of both criteria.

Animals↗
PubMed1983

Relationship of somatomedin-C concentrations to pubertal changes.

The plasma somatomedin-C concentration increases above adult values during the teenage years. We studied the relationship of pubertal variables and the adolescent growth spurt to the changes in plasma total Sm-C concentration in normal volunteers and in boys with delayed puberty. The rise in plasma Sm-C concentrations was gradual and correlated positively with pubertal variables rather than with age. By midpuberty, plasma Sm-C had usually risen twofold. The Sm-C level in midpubertal girls (3.1 +/- 1.1, SD, U/ml) was greater than that in midpubertal boys (1.9 +/- 0.50, P less than 0.05). The Sm-C concentration in sexually mature teenagers was two to three times greater than that of adults. Both estrogens and androgens correlated independently with the plasma Sm-C concentration. The data are compatible with the hypothesis that pubertal estrogen or testosterone levels cause an increase in Sm-C, an effect possibly mediated by stimulation of growth hormone secretion, whereas greater estrogen exposure inhibits Sm-C generation, possibly by a direct effect. Plasma Sm-C concentrations correlated significantly with linear growth velocity until the age of peak pubertal growth velocity. Maximum Sm-C values were observed after the peak pubertal growth velocity was achieved, as height velocity was decelerating, and remained above adult levels for at least two to six years, at which time linear growth had virtually ceased. In boys with delayed puberty, Sm-C values resembled those of boys of like pubertal stage more closely than those of boys of similar age. Depressed plasma Sm-C values were found in some boys with delayed puberty; however, these did not preclude subsequent normal linear growth during sexual maturation.

Adolescent↗
PubMed1976

Individual growth in stature: a comparison of four growth studies in the U.S.A.

Patterns of growth in stature of subjects from the four major U.S. longitudinal growth studies are compared by means of a two-component model for individual growth. Problems inherent in the comparison of data from independent growth studies, such as those arising from different methods of sampling subjects and scheduling measurements and the occurrence of atypical subjects, are considered and solutions are offered. Statistical tests of the individual growth parameters revealed significant, but small, differences among the samples in the magnitude of the contributions of prepubertal and adolescent growth to mature stature and in the velocity of growth. No differences between samples in the timing of the adolescent component were detected.

Adolescent↗