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Biomedical subjects

F Hu

Publications and source records attributed to F Hu.

At least 73 records · Page 4Linked to original sources
PubMed1993

A unique, predominant hepatitis C virus variant found in an infant born to a mother with multiple variants.

To demonstrate vertical transmission of hepatitis C virus (HCV) from an HCV-infected, non-human immunodeficiency virus type 1-infected mother to her infant and to assess the distribution of viral species in the mother and infant, the hypervariable region of the gene encoding the putative envelope glycoprotein E2 (E2HV) was sequenced in three mothers and one mother-infant pair. The data indicate that (i) quasi-species distributions of HCV E2HV variants were found in all four mothers, (ii) a single predominant HCV E2HV variant was found in the infant of a mother shown to have nine predominant E2HV variants, and (iii) the infant's E2HV variant was highly related to, but not identical with, the nine variants identified in the mother at the time of birth. These findings indicate that HCV is transmitted from mother to infant and raise the possibility that the transmission occurs in utero.

Amino Acid Sequence↗
PubMed1992

Optimal diaphragmatic blood perfusion.

The intrabreath time course of phrenic artery blood perfusion (Qpha) was studied in five anesthetized dogs. The diaphragm was paced with submaximal levels of stimulation at various duty cycles (DC) to achieve tension-time index below and above the fatigue threshold (0.03-0.60). Left Qpha was measured via Doppler technique during control (inactive diaphragm) and during two submaximal levels of bilateral phrenic nerve stimulation sustained for 1 min. Measurements were done when Qpha reached steady state in each run. The frequency of pacing of each run was 10/min, and the DC ranged from 0.1 to 0.9 in 0.1 increments. Shortening of costal and crural segments was measured by sonomicrometry. It was found that Qpha during the diaphragmatic contraction phase (QphaC) was a sigmoidal function of DC and was not affected by the levels of transdiaphragmatic pressure (Pdi) explored (34-64% of maximal Pdi). Qpha during the diaphragmatic relaxation phase (QphaR) was a parabolic function of the DC, reaching an optimal value at DC of approximately 0.3 at any given Pdi. QphaR increased significantly with the preceding level of Pdi. QphaT (the sum of QphaC and QphaR) was a parabolic function of DC, reaching peak values at DC of 0.4-0.6 and then decreasing. This function was similar at two levels of Pdi. Post-pacing hyperemia was directly related to tension-time index greater than 0.20.

Animals↗
PubMed1991

Restriction of regional blood flow and diaphragmatic contractility.

We have tested the hypothesis that the diaphragmatic head-to-head arterial anastomosis system should maintain adequate diaphragmatic function even during occlusion of some of its arteries. In six anesthetized open-chest dogs, left phrenic vein blood flow (Qphv) was measured by pulsed Doppler flowmetry. Contractility was measured by sonomicrometry in the left costal and crural diaphragm. The diaphragm was paced for 15 min by continuous bilateral supramaximal phrenic nerve stimulation. In five separate runs the following arteries were occluded at minute 5: 1) left phrenic artery, 2) internal mammary artery (IMA), 3) left phrenic artery and IMA, 4) descending aorta, and 5) descending aorta and IMA. Occlusion was then released at minute 10 of the run. In runs 1-3 there were no changes in contractility in costal or crural diaphragm and no changes in Qphv. However, in runs 4 and 5, Qphv decreased to 55.2 +/- 7.4 and 24.0 +/- 6.5% of control values, respectively. In run 4, percent maximum shortening from functional residual capacity (%LFRC) of the crural diaphragm decreased by 39.1%, while %LFRC of the costal diaphragm increased by 41.4% and abdominal pressure decreased by 47.0%. In run 5, abdominal pressure decreased by 53.5% and %LFRC of the crural and costal diaphragm decreased by 45.5 and 5.8%, respectively. Also relative postocclusion hyperemia was greater in run 5 (64.8%) than in run 4 (40.2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Contraction-dependent modulations in regional diaphragmatic blood flow.

Blood flow (Q) of the diaphragm was measured simultaneously with Doppler probes placed on diaphragmatic veins and an artery and by direct volumetric measurements obtained from cannulation of diaphragmatic blood vessels. The Doppler converting coefficients obtained were 6.27, 7.25, 4.21, and 41.07 ml.min-1.kHz-1 for left phrenic artery flow (Qpha), phrenic vein flow (Qphv), internal mammary vein flow (Qimv), and azygos vein flow (Qazv), respectively. The time course of Qpha, Qphv, Qimv, and Qazv after imposed patterns of diaphragmatic contraction was measured in nine anesthetized dogs. Each pattern consisted of various combinations of transdiaphragmatic pressure (Pdi), frequency of pacing (f), and duty cycle obtained by bilateral phrenic nerve stimulation. The dogs were prepared with chests open and loosely casted abdomens. Qpha, Qphv, Qimv, and Qazv were measured at rest (control, passive diaphragm, mechanical ventilation) and at two submaximal levels of stimulation (30 and 60% of Pdimax). The f was 10 or 30 cycles/min and the duty cycle was 0.25, 0.50, and 0.75. The results show 1) Qpha, Qphv, Qimv, and Qazv reached stable values (equilibration) after 30-36 s of pacing; 2) the steady Qpha, Qphv, and Qimv were linearly related to Pdi, and they were related by a parabolic function to duty cycle, whereas Qazv was not significantly affected by Pdi and increased linearly as a function of the duty cycle; 3) the diaphragmatic blood drainage was approximately 60% through the intercostal veins leading into the azygos trunk, 25% through the phrenic vein, and 15% through the internal mammary vein during pacing of the diaphragm at a duty cycle of 0.50 and 60% Pdimax; and 4) for a given pacing pattern, Qpha and Qphv increased with f, but Qimv and Qazv did not.

Animals↗
PubMed1990

Effect of separate hemidiaphragm contraction on left phrenic artery flow and O2 consumption.

Phrenic arterial blood flow has been shown to increase during bilateral phrenic nerve stimulation (BPNS). However, the role of unilateral phrenic nerve stimulation [left (LPNS) or right (RPNS)] on the blood flow and O2 consumption of the contralateral hemidiaphragm is not known and is explored here. In six anesthetized, mechanically hyperventilated dogs, left phrenic arterial blood flow (Qlpha) was measured (Doppler technique). Supramaximal (10 V, 30 Hz, 0.25-ms duration) LPNS, RPNS, and BPNS at a pacing frequency 15/min and duty cycle of 0.50 were delivered in separate runs. Left hemidiaphragmatic blood samples for gas analyses were obtained by left phrenic venous cannulation. During RPNS, Qlpha and left hemidiaphragmatic O2 consumption (VO2ldi) did not change significantly compared with control. During LPNS and BPNS, there was a significant increase in Qlpha and VO2ldi (P less than 0.01). There was no significant difference in Qlpha and VO2ldi between LPNS and BPNS (P greater than 0.05). We conclude 1) that there is a complete independence of left-right hemidiaphragmatic circulation both at rest and during diaphragm pacing and 2) that during unilateral stimulation transdiaphragmatic pressure is not related to diaphragmatic blood flow.

Animals↗
PubMed1990

Intravenous tryptophan tolerance test for liver function.

An intravenous tryptophan tolerance test (ITrpTT) was designed for liver function since 95% Trp is metabolized by the liver. After an intravenous loading dose of 4 mg/kg body weight, serum levels of both free (F) and total (T) Trp were determined at 45 and 60 minutes. In normal controls and nonhepatic-disease patients, F45 (60) and T45 (60) did not exceed 7 mumol/L and 80 mumol/L, respectively, and F/T ratio not greater than 0.14. These were set up as cutoffs of upper normal limits. The test was abnormal in 87.5% of chronic persistent hepatitis (CPH) characterized by elevation of T45 (60), 100% of chronic active hepatitis (CAH) by elevation of F45 (60) and/or T45 (60), and 100% of hepatic cirrhosis by increase in F45 (60) and F/T ratio but not in T45 (60). The test seems to be more sensitive than the conventional tests for liver function. However, one should be cautious in interpretation of the test as there are some factors which might influence the Trp metabolism like exercise, alcoholism, corticosteroids and enzyme-inducers. It merits as an indication of liver dysfunction only when these factors are considered and excluded.

Adult↗
PubMed1988

Plasma 5-S-cysteinyldopa correlates with tumor size in melanoma-bearing mice.

A sensitive assay method employing high performance liquid chromatography with electrochemical detection (HPLC-ED) was used to compare 5-S-cysteinyldopa (CD) levels in plasma to tumor size in a murine melanoma model system. Plasma CD levels correlated with the sizes of primary tumor masses in mice, and the presence of metastatic tumors did not significantly affect the relationship. Elevated plasma CD levels appear to be directly related to tumor pigmentation: mice who had nonpigmented tumors induced by injections of amelanotic melanoma cells (NP) did not have elevated plasma CD levels. These studies indicate that plasma CD levels may serve as a marker for pigmented malignant melanomas and may be useful in following patients who are at high risk for these tumors.

Animals↗
PubMed1987

Normal uveal melanocytes in culture.

Normal uveal melanocytes of rhesus and cynomolgus macaques can be grown in culture for 3-9 months and subcultured a few times. Postnatal and adult choroidal melanocytes are terminally differentiated cells. They are melanin-containing but not actively melanin-synthesizing cells. They do not undergo cell division, nor do they incorporate tritiated thymidine, but otherwise they are metabolically active. Postnatal and young adult iridial melanocytes are metabolically more active than choroidal cells. They require a feeder cell layer for attachment and to be maintained in a healthy condition. An endothelial cell line established from a rhesus fetal choroid-retina proves to be an effective feeder layer for adult iridial cells. Fetal uveal melanocytes divide slowly and usually require some stimulus and a special culture environment supplemented with 12-O-tetradecanolphorbol-13-acetate and cholera toxin. They can grow and differentiate in vitro. Iridial melanocytes grow and change into cells resembling postnatal choroidal melanocytes. Similar changes occur during development in utero. These findings further suggest that, in vivo, iridial melanocytes migrate and mature to become choroidal melanocytes.

Aging↗
PubMed1987

Theophylline effects on normal uveal melanocytes in culture: an ultrastructural study.

Theophylline enhances maturation and differentiation of uveal melanocytes. By electron microscopy, we showed that theophylline changes small, dendritic melanocytes into large, platelike cells; it also enhances DOPA reaction as evidenced by increased deposition of DOPA reaction products in dilated cisternae and vesicles around the Golgi region. The effect is partially reversible in choroidal melanocytes but irreversible in iridial cells. It appears that theophylline, in addition to inducing tyrosine activity, accelerates the maturation and/or aging that normally occurs in cultured melanocytes when incubation is prolonged.

Animals↗
PubMed1986

Gossypol effects on cultured normal and malignant melanocytes.

Gossypol, a polyphenolic compound known to interfere with spermatogenesis, was found to have differential cytotoxic effects on normal and malignant melanocytes in culture. Ultrastructurally it caused marked swelling and vacuolization of mitochondria; there was an almost complete loss of cristae but the outer mitochondrial membrane was retained. The cytotoxicity seemed to be selective for actively proliferating cells, regardless of normal or malignant origin. An endothelial cell line (RF/6A) derived from the choroid-retina of the eye of a rhesus fetus was extremely sensitive to its toxic effect. The mechanism of action is still unknown. The fact that mitochondria are predominantly damaged suggests that toxicity involves a perturbation of energy metabolism and the membrane transport system.

Animals↗
PubMed1986

Effects of dicarboxylic acids on normal and malignant melanocytes in culture.

We have shown that dicarboxylic acids (C9 and C12), known competitive inhibitors of tyrosinase, are selectively cytotoxic to malignant melanogenic melanocytes but not to normal pigmented cells or to amelanotic or non-melanogenic melanoma cells. The main target of this toxicity appears to be the mitochondria, which become markedly swollen and vacuolated. The mechanism of their action has been thought to be due to interference with oxidoreductases in the mitochondria. However, our results suggest that this cytotoxicity most probably does not result simply from inhibition of mitochondrial enzymes, but is closely related to the melanin biosynthesis pathway.

Animals↗
PubMed1985

Dermal melanocytes and elastic fibers.

The relationship between dermal melanocytes and elastic fibers was studied by electron microscopy. In 3 patients with dermal melanocytosis, the long cytoplasmic processes of the melanocytes were aligned along the long axis of the elastic fiber, and encircled or embraced these fibers. The same intimacy existed between melanocytes and elastic fibers in the skin of cynomolgus macaques, who normally have dermal melanocytes. These findings suggest that dermal melanocytes, for reasons yet to be determined, interact with elastic fibers under these special conditions.

Aged↗
PubMed1984

Dermal Merkel cells in the nevus of Ota and leopard syndrome.

We observed dermal Merkel cells around vellus hair follicles in one patient with nevus of Ota and one with leopard syndrome. These Merkel cells were in contact with Schwann cells and nerve endings in the dermis. The question of whether or not Merkel cells exist normally in adult dermis remains unanswered. However, their presence in these abnormal conditions suggests that normally they do occur in the dermis but go undetected because their numbers are so few or they are in a form not readily identifiable by currently available methods.

Abnormalities, Multiple↗