Search PubMed⌕ Search

Biomedical subjects

L Dong

Publications and source records attributed to L Dong.

144 records · Page 8Linked to original sources
PubMed1986

Development of physiological responses to acetylcholine during organ culture of young embryonic chick hearts.

Young (3 days-old) embryonic chick hearts (i.e., prior to innervation) have a low sensitivity and transient response to acetylcholine (ACh). In the present experiments, in which the hearts were placed into organ culture for a period of up to 7 days, the sensitivity to ACh was found to increase with time in culture, and the inhibitory action of ACh persisted for a longer time (i.e., desensitization declined). Thus, the ability to ACh to slow spontaneous heart rate and to shorten action potential duration (in the atrium) became greater during the course of organ culture. The effects of ACh on spontaneous heart rate and on action potential duration were blocked by atropine. These results suggest that the physiological responses to muscarinic agonists in young embryonic chick hearts continue to develop in organ culture, and that the increased sensitivity to muscarinic agonists seen in ovo is unlikely to be due to the development of innervation.

Acetylcholine↗
PubMed1985

The endocrinological profile of normal menstrual cycles in a population of Chinese women.

Endocrinological profiles of normal menstrual cycles were studied in 41 Chinese women. Daily serum concentration of luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL), estradiol (E2) and progesterone (P) were determined by RIA. Thirty-four cycles were of normal length (26-35 days) and 6 cycles were prolonged up to 40 days with a follicular phase of 22-26 days. One cycle was anovulatory. Cyclical changes of LH, FSH, E2 and P were typical of ovulatory cycles in other populations as reported in the literature. In the normal cycle group the geometric mean of the LH midcycle peak level was 46 IU/1, the FSH peak was 10 IU/1, the preovulatory estradiol peak was 1229 pmol/1 and the progesterone luteal maximum was 50 nmol/1. The pattern of cyclical changes in the prolonged ovulatory cycles was similar to the normal length cycles, except that there were significantly higher levels of LH in both follicular and luteal phases, lower FSH in luteal phase, and lower progesterone in luteal phase. A majority of cycles had a midcycle elevation of prolactin and mean PRL levels in the late luteal phase were higher than those in the follicular phase.

Adolescent↗
PubMed1980

Clearance of liquid from lungs of newborn rabbits.

Apparent inconsistencies in the results of previous studies led us to reexamine the process by which fluid leaves the lungs of newborn rabbits after birth. We measured pulmonary blood volume, extravascular lung water, and the size of perivascular cuffs of fluid in frozen sections of lung obtained from 166 full-term rabbits (31 days gestation) born vaginally or by cesarean section. We killed the rabbits by giving them barbiturate intraperitoneally and immersing them in liquid nitrogen before they breathed or at randomly predetermined intervals from 5 min to 24 h after birth. We found that a) pulmonary blood volume of both groups of rabbits increased soon after birth, b) extravascular lung water per gram of dry lung tissue was greater at birth in rabbits born by cesarean section than in those born vaginally, c) extravascular lung water did not begin to decrease in either group of animals until 30-60 min postnatally, after which it decreased progressively for 24 h, and d) the rate of fluid clearance and pattern of puddling around pulmonary vessels was similar in both groups of rabbits, with maximal perivascular cuffs 30 min after birth, followed by diminution of cuff size as the lungs shed water.

Animals↗
PubMed1977

The effect of time of cord clamping and maternal blood pressure on placental transfusion with cesarean section.

We measured the residual placental blood volume (RPBV) of 20 infants delivered at term by cesarean section of women not in labor. In all cases, the umbilical cord was clamped within 40 seconds of birth. RPBV decreased significantly with increasing age at cord clamping. In addition, RPBV for infants with cords clamped within 20 seconds of birth correlated inversely with maternal systolic blood pressure (mean RPBV = 54.8 ml. per kilogram at 105 torr and 28.4 ml. per kilogram at 148 torr). However, RPBV did not correlate with maternal blood pressure for the whole group of 20 infants or for those with cords clamped later than 20 seconds after birth. These data indicated that in infants delivered by cesarean section placental transfusion is time related during the first 40 seconds of life and that maternal blood pressure also influences the magnitude of placental transfusion during the first 20 seconds after birth. Analysis of data from this study combined with data from a previous study shows that after 40 seconds the net flow between placenta and infant reverses and that cord clamping delayed beyond this point is accompanied by a rise in RPBV back to the level found when the cord was clamped before 20 seconds.

Blood Pressure↗
PubMed1976

A volume-displacement plethysmograph to measure limb blood flow in the newborn infant.

An instrument is described that measures limb blood flow in newborn infants by venous occlusion plethysmography. The plethysmograph is filled with air and a pneumotachygraph measures the volume displaced during venous occlusion. The response of the system is linear for flows over the range 1 to 100 ml/min and the frequency response to a square wave pressure change is 22 Hz with a 95% response time of 0.5 second. The average flow in the forearm of 10 normal newborn infants was 5.9 ml/min per 100 ml of tissue.

Blood Flow Velocity↗
PubMed1975

Cesarean section prevents placenta-to-infant transfusion despite delayed cord clamping.

We have adapted and calibrated an accurate method for measuring residual placement blood volume (RPBV). We used this method in 33 normal vaginal deliveries and 18 cesarean section deliveries in which the umbilical cord was clamped from 5 to 118 seconds after delivery. Infants born vaginally received 10 to 20 ml. per kilogram of body weight of placental transfusion when umbilical cord was not clamped until 30 seconds or more after delivery. Equivalent delay of umbilical cord clamping in cesarean section infants produced no placental transfusion.

Birth Weight↗
PubMedDate not supplied

Reversible and irreversible immobilization of enzymes on Graphite Fibrils.

Graphite Fibrils are hollow tubes (0.01 x 1-10 microns) consisting of concentric layers of graphite. Fibrils can be chemically modified to introduce surface functionalities such as carboxyl groups. Carboxylated fibrils were further functionalized to amino alkyl derivatives which were covalently linked to an enzyme, horseradish peroxidase (HRP). HRP fibrils showed substantial catalytic activity. Additionally, carboxyl fibrils were derivatized with specific inhibitors of the enzymes beta-galactosidase (beta-Gal) and alkaline phosphatase (AP). Enzyme inhibitor-modified fibrils were used to specifically purify both beta-Gal (using beta-Gal inhibitor fibrils) and AP (using AP inhibitor fibrils) from mixtures of these two enzymes. These studies demonstrate the feasibility of using Graphite Fibrils as supports in biocatalysis and biospecific affinity chromatography.

Alkaline Phosphatase↗
PubMedDate not supplied

Systemic uptake and clearance of chloroform by hairless rats following dermal exposure: II. Absorption of the neat solvent.

Blood concentrations of chloroform were monitored after exposing small areas (approximately 5.5 cm2) of the backs of hairless rats to liberal excesses of the solvent for either 1, 3, or 8 min. The amounts absorbed were quantified by comparing areas-under-the-curves (AUCs) of blood concentration versus time plots to the AUC obtained on infusing an aqueous chloroform solution of known concentration for 30 min (positive control). Chloroform penetrated the dermal barrier rapidly, the skin's horny layer and the deeper skin tissues acting as reservoirs for chloroform only for short durations. Evaporative and physiological clearance from these reservoirs was rapid once the chloroform was removed from the surface. Pressure of the template used to confine the exposure affected uptake. For blood levels, the time to reach the maximum blood concentration increased with increased exposure duration. Amounts absorbed also depended on exposure duration. Blood level profiles indicated systemic uptake of chloroform following a 3-min exposure was about 1.3-fold higher than for a 1-min exposure (not significant), while the 8-min exposure produced an AUC roughly 3.8-fold higher than found at 3 min (p = 0.026). Chloroform is rapidly cleared from rat blood (terminal elimination rate constant = 0.009/min). Calculations indicated that its absorption from these area-limited exposures far exceeds that which would be absorbed had the chloroform been presented to the skin as a saturated aqueous solution.

Administration, Cutaneous↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part I--General considerations and summary of results.

Recurrent plantar ulceration is a common and serious complication occurring consequent to impairment of the tibial nerve in leprosy patients. In spite of many therapies and long therapeutic course, it is extremely difficult to abolish this complication in many cases because of extensive skin and soft tissue cushion loss due to repeated infection. Since the early 70's we have been using microscopic surgical techniques to reconstruct the ulcerated area using eight types of the flaps. In this series of papers we review our experience (76 patients). Post-operatively, the flaps survived in all cases, the long-term results have proved satisfactory, and recurrent ulceration occurred in only three patients.

Adult↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part II--First toe web and dorsal foot flaps.

The first toe web flap consists of the skin and subcutaneous tissues of the contiguous sides between the great and second toes. It is based on the first dorsal metatarsal artery or the common plantar digital artery. This flap was used as artery pedicled island graft to reconstruct losses of skin and soft tissue cushion in the ball of the foot in the first and second metatarsal head region in 16 cases. Follow-up examination revealed that ulceration had recurred in one case due to dehiscence of the flap margin 12 months post-operatively. The other 15 patients have done well without recurrence at 48 to 124 months follow-up examination. The dorsal flap of the foot based on the dorsalis pedis artery, the corresponding veins and the deep peroneal nerve was designed in 1974 to resurface skin and soft tissue defects in the sole of the foot. This flap was used in 30 cases of leprosy with excellent results. During follow-up 36 to 120 months after surgery the plantar ulcer had recurred in only one case. All the others have done well. The long-term curative effect has thus proved satisfactory.

Foot Ulcer↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part III. Use of plantar skin or musculocutaneous flaps and anterior leg flap.

Anatomical studies suggest that five types of plantar flaps namely, the lateral and medial plantar flaps, the Abductor hallucis-, the Flexor digitorum brevis-, and the Abductor digiti minimi-myocutaneous flaps, can be incised from the central section of the sole. The advantages of a plantar flap are recognizable neurovascular bundles of the sole, wide calibre of constantly located blood vessels, identical histological structure of the donor and the recipient sites, hidden donor site and absence of functional deficit. We have used the plantar flaps in seven cases. There has been no recurrence of ulceration in any of them during the follow-up period of 12 to 108 months. An anterior leg flap based on the cutaneous branches of the anterior tibial artery, with firmly anchored vessels, a long pedicle with wide vessels may be used not only as a free flap graft for reconstruction of moderate degree distant defects but also as a retrograde island flap graft for the reconstruction of adjacent tissue defect. We have used the retrograde island flap graft based on the anterior tibial artery in five cases of plantar ulceration with satisfactory results. There was no recurrence of ulceration during the follow-up period of 48 to 72 months.

Foot↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part IV. Use of medial leg flap and medial knee flap.

The medial leg flap, based on the cutaneous branches of the posterior tibial artery is raised from the middle and lower regions of the medial aspect of the leg. It has a long pedicle, and it can be used as a free flap to reconstruct the distant soft tissue defects and also as an island flap. We have used this retrograde island flap for surfacing ulcerated areas in six leprosy patients. The flap survived in all cases. At 24 to 60 months follow-up examination, ulceration had not recurred in any of them. The medial knee flap consisting of the skin and subcutaneous tissue of the lower part of the medial side of the thigh and the upper part of the leg, is suitable for covering soft tissue cushion defects of the extremities because of the constant vessels, long pedicle, wide diameter, well-recognizable sensory nerves and less subcutaneous fat. We have used the medial knee flap for the resurfacing sizeable raw areas due to ulceration in three leprosy patients. The flap survived in all cases and there was no recurrence of ulceration during the 70-148 months follow-up period.

Foot Ulcer↗
PubMedDate not supplied

Techniques for covering soft tissue defects resulting from plantar ulcers in leprosy: Part V. Use of the flap in the inguinal region and latissimus dorsi musculocutaneous flap.

The area of distribution of the superficial circumflex iliac, superficial epigastric and superficial external pudental arteries is large and flaps based on them can meet the requirement of different recipient sites. We have transplanted free flaps based on the superficial epigastric artery for repairing plantar soft tissue defects in six leprosy patients. During the follow-up examination 58 to 118 months later there has been no recurrence of ulceration in any of these cases. The latissimus dorsi muscle, is mainly nourished by the thoracadorsal artery and the latissimus dorsi musculocutaneous flap is a large sized, composite structure with abundant blood provision and strong anti-infectious property. The latissimus dorsi flap can be used as an artery-pedicled island flap or as a free flap besides its use as a muscle graft, because of its constant vascular position, wide outer-diameter of the vessels and long pedicle. It can therefore be utilized for repairing soft tissue defect or replacement of paralyzed muscle. We have used the latissimus dorsi musculocutaneous free flap for repairing large skin and soft tissue defects resulting from plantar ulceration in three leprosy patients. During the follow-up period, one patient who had complete drop-foot and had refused corrective surgery had recurrence of the ulcer in the 12th post-operative month. No ulcers had recurred in the other two cases during the follow-up at 48 and 114 months.

Foot Ulcer↗
PubMedDate not supplied

Transplantation of fibula with vascular pedicle for fusion of ankle in leprotic drop-foot.

Devascularized bone grafts are pieces of dead bone and they simply serve as scaffolds for new bone to grow and fill the gap, taking a long time when they succeed in doing so. In contrast, vascularized grafts being living tissues have short healing time, great vitality and strong infection-resisting capacity. We report here the successful use of vascularized grafts of the lower end of fibula for fusing the ankle in five leprosy patients.

Adult↗