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Biomedical subjects

B Chen

Publications and source records attributed to B Chen.

At least 505 records · Page 28Linked to original sources
PubMed1991

[Comparison between pulmonary vascular pathology and hemodynamics in congenital heart disease with pulmonary hypertension].

The relation between pulmonary vascular pathology and hemodynamics in 81 patients with congenital heart disease complicated by pulmonary hypertension was studied. Slight to marked increase of mean pulmonary pressure (MPAP) was seen in 5 of them, but no vascular lesion was found. 59 of the 81 cases had marked increase of MPAP and Grade 1-2 pulmonary vascular lesions, and cyanosis was seen clinically. Postoperative effects were satisfactory, indicating that not all patients with cyanosis contraindicated surgical treatment. The rest (17) of the 81 patients had most marked increase of MPAP and Grade 3-4 pulmonary vascular lesions with good postoperative results, but long-term results await follow-up observations. It is thought that Grade 4 pulmonary vascular lesion should be considered as a contraindication for corrective surgery.

Adolescent↗
PubMed1990

Biochemical consequences of phosphorylcholines low pK with special relevance to human semen: passive pH regulation.

1. The significant difference in pK between phosphorylcholine (PCh) and inorganic phosphate (Pi) of over 1 pH unit results in PCh being a source of acid buffering potential and an actual sink for protons when it is hydrolyzed. Phosphorylethanolamine (PEth) can fill the same role. 2. Both semen and tissues having substantial anaerobic metabolism among which are those of fetal origin can face circumstances of non-pathological acidosis. 3. We demonstrate from the literature that all of those tissues with the two understandable exceptions of erythrocytes and striated muscle, have high levels of PEth and/or PCh. 4. Since these phosphomonoesters can serve as lipid metabolites as well as low-pK fixed-phosphate buffer it appears they can serve a dual function in these tissues. 5. Their concentration would vary depending on the physiological and biochemical conditions present and we would call this a "Swiss army knife" theory of metabolic function.

Alkaline Phosphatase↗
PubMed1990

Inhibition of TPA-induced monocytic differentiation in THP-1 human monocytic leukemic cells by staurosporine, a potent protein kinase C inhibitor.

THP-1 is a factor-indepencent, monocytic leukemia cell line which differentiates into adherent macrophages upon treatment with 12-O-tetra-decanoylphorbol-13-acetate (TPA). Unlike its normal counterparts, THP-1 cells display only minimal levels of proto-oncogene c-FMS RNA which encode for membrane M-CSF receptors. Northern blot analysis showed that the c-FMS mRNA levels in THP-1 cells was greatly enhanced during TPA-induced monocytic differentiation. Despite the acquisition of functional activities and induction of c-FMS transcripts after TPA treatment, no surface M-CSF receptors were detected on the THP-1 cells. The inducing activity associated with TPA was completely abrogated when THP-1 cells were pretreated with staurosporine, a potent protein kinase C (PK-C) inhibitor. It is concluded that the activation of the PK-C system is a part of the metabolic cascade essential for the initiation of monocytic differentiation in THP-1 cells.

Alkaloids↗
PubMed1990

A phase I trial of recombinant interleukin-2 combined with recombinant interferon-gamma in patients with cancer.

Twenty-six patients with metastatic cancer were entered into a phase I trial of concurrent recombinant interleukin-2 (IL-2) and recombinant interferon-gamma (IFN-gamma). IL-2 was administered as a continuous intravenous infusion for 5 days. IFN-gamma was administered by a daily intramuscular (IM) injection during the 5 days of IL-2 administration. Treatment was repeated twice after 9-day rest periods. After a 2-week rest, patients without evidence of tumor progression were retreated. Natural killer (NK)- and lymphokine-activated killer (LAK)-cell activity were assayed in each patient before treatment, on day 1, and on day 5 of each cycle. Constitutional symptoms occurred in most patients but were not dose-limiting. Other toxicities included hypotension responsive to fluids, transient elevations in liver function tests, erythema/pruritus, eosinophilia, and transient leukopenia/thrombocytopenia. The maximum-tolerated dose (MTD) of the combination was 1 x 10(6) U/m2/d of IL-2 combined with 0.50 mg/m2/d of IFN-gamma. The dose-limiting toxicity was pulmonary manifesting as rales and shortness of breath. The dose of the combination that resulted in the optimal generation of in vivo LAK-cell activity was a dose of at least 0.25 mg/m2/d of IFN-gamma combined with 1 x 10(6) U/m2/d of IL-2. Objective clinical responses were seen in five of 26 patients. These included a partial response of 2 months duration in a patient with non-Hodgkin's lymphoma (NHL), mixed responses in a patient with NHL and two patients with renal cell carcinoma (RCC), and an ongoing assessable response in a patient with bone metastases from RCC. The recommended dose for phase II trials of this combination is 0.50 mg/m2 of IFN-gamma and 1 x 10(6) U of IL-2.

Adolescent↗
PubMed1990

[Study on the coated carbon PVC membrane selective electrode of aconitine].

Coated carbon PVC membrane selective electrode of aconitine was prepared with the Aconitine-tetraphenylborate ion-associate complex as the electroactive material. The electrode showed a linear response to aconitine within the concentration range 1.0 x 10(-2) - 5.0 x 10(-5) mol/L. The limit of detection was 6.3 x 10(-6) mol/L and the slope of the electrode was 57.6 mV/decade. The authors established a basis and a method for the control of content limit of aconitine in Shen Fu Injection with this electrode.

Aconitine↗
PubMed1989

Spatial organization of sensitivity regulation in rod vision.

To investigate whether scotopic sensitivity is set locally or in neural "pools", we have tested the spatial variation in sensitivity after bleaching with gratings using 3 different methods. One experiment circumvented the influence of involuntary eye movements by deliberately randomizing the horizontal position of a fine test line on the area bleached by the vertical gratings. The spatial variation of threshold across the bleached area is reflected in the width of the frequency-of-seeing curve. A clear difference between the probability-of-seeing curves following a grating bleach and a uniform bleach was seen only up to between 4.2 and 6.3 c/deg, suggesting that adaptation signals are pooled so as to almost obliterate the contrast in finer gratings than this. In a second experiment the lowest bleaching-grating contrast (for a space-averaged initial rhodopsin bleach of 10%) that produced a patterned afterimage stayed close to the scotopic threshold contrast for frequencies from 1 to 6.4 c/deg, but it rose above the contrast threshold at high spatial frequencies. This slight loss of sensitivity at the high frequencies is more evidence for pooling in adaptation. A third experiment assessed the sensitivity profile at the adapting site without any influence of later stages of neural integration. Bleaching and test gratings of slightly different spatial frequency were flashed successively. If the effect of bleaching is restricted to the bleached rods, the observer will effectively be looking at the test grating through a grid of sensitive and insensitive stripes in his own retina. The two gratings come in and out of register at the difference frequency, and a corresponding low-frequency grating should be visible even when the test and bleaching gratings are not themselves resolved by the later stages. We could not see the difference frequency unless the test and bleach gratings were themselves coarse enough to be resolvable in rod vision. This is very strong evidence against any model in which each rod has its own sensitivity-regulating mechanism, and instead supports (for these conditions) Rushton's view that adaptation is entirely the work of a neural pool. The estimated pool size is about 10 min arc of visual angle.

Adaptation, Ocular↗
PubMed1989

Vasoactive intestinal peptide (VIP) may reduce the removal rate of cytosolic Ca2+ after transient elevations in clonal rat lactotrophs.

The prolactin-producing rat anterior pituitary GH4C1 cells possess Ca2+-activated K channels which are activated by physiological elevations of the cytosolic Ca2+ concentration even at membrane potentials more negative than the normal level of about -50 mV. Whole-cell current recordings showed a marked outward tail current following depolarizing voltage steps to 0 mV from a holding potential close to the normal membrane potential. The half-time of this tail current was about 1.3 s after a 4-s depolarization step. The GH4C1 cells also possess voltage-activated Ca channels, and we conclude that this tail current is a Ca2+-activated K+ current for the following reasons: (1) The reversal potential for the tail current was close to the K+ equilibrium potential for a range of transmembrane K+ gradients. (2) The tail current was blocked by a Ca2+ antagonist, and the voltage dependence of this current closely mirrored the voltage dependence of the isolated Ca2+ current. The time-course of the decline of the tail current thus reflects the removal rate of the Ca2+ entering the cytosol through voltage-dependent Ca channels during the depolarizing voltage step. VIP stimulates prolactin secretion from GH4C1 cells, and this peptide prolonged the half-time of the tail current by about 47% in 63% of the cells. This indicates that VIP may prolong the transient cytosolic Ca2+ elevations following the action potentials in these cells. Such a mechanism might be an important factor for the control of the cytosolic Ca2+ level, and hence hormone secretion.

Animals↗
PubMed1989

Light capture by human cones.

1. The variation in visual efficiency of light with varying pupillary entry (the Stiles-Crawford effect) was measured to determine the proportion of light incident on the cones that escapes them without recovery by other cones. 2. The variation in detectability of interference fringes with varying pupillary entry of the interfering beams was measured to determine the proportion of incident light that was recaptured by cones in the dark stripes after escaping cones in the bright stripes of the fringes. 3. By exclusion, these observations determine the variation, with varying pupillary entry, in the proportion of incident light that was captured and absorbed by the first cones it entered. 4. Some 70-90% of the light absorbed by the cones when it passes through the centre of the pupil, is entirely lost to the visual system if it passes instead through the margin of the (dilated) pupil. 5. Over half the light that cones absorb when the light enters the margin of the pupil is light that has previously passed through other cones. 6. If the spread of recaptured light is assumed to be Gaussian, its standard deviation is at most one minute of visual angle. 7. Such recaptured light makes a previously unknown contribution to the various Stiles-Crawford effects.

Humans↗
PubMed1989

The effect of diazepam on neonatal seizure: in vivo 31P and 1H NMR study.

It is assumed that when anticonvulsants arrest seizure, there is rapid return of brain high energy phosphates and brain lactate to control values. To test this hypothesis, diazepam was administered to neonatal dogs during flurothyl-induced seizure. In vivo 31P nuclear magnetic resonance spectroscopy disclosed that diazepam quickly arrested electrographic seizure and restored brain phosphocreatine and inorganic phosphate to baseline values. In contrast, in vivo 1H nuclear magnetic resonance spectroscopic measurements showed that arrest of seizure with diazepam did not return brain lactate to control values. The sustained increase in cerebral blood flow and prolonged elevation of brain lactate, acetate, valine, and succinate in the postictal period indicate that metabolic recovery of the brain occurs over an extended period of time after the normalization of EEG, phosphocreatine, and brain pH.

Acetates↗
PubMed1989

Environmental factors and Parkinson's disease: a case-control study in China.

We studied the role of environment in the development of Parkinson's disease (PD) in China, where industrialization is relatively recent and the population geographically stable. Using a case-control method, we investigated the relationship between PD and exposure to the following factors before disease onset: place of residence, source of drinking water, environmental and occupational exposure to various agricultural and industrial processes. Occupational or residential exposure to industrial chemicals, printing plants, or quarries was associated with an increased risk of developing PD. In contrast, living in villages and exposure to the common accompaniments of village life, wheat growing and pig raising, were associated with a decreased risk for PD. PD cases and controls did not differ with respect to other factors investigated. These findings are consistent with the hypothesis that environmental exposure to certain industrial chemicals may be related to the development of PD.

Adult↗
PubMed1989

The relationship between serum lipid levels and nutrient intake in healthy inhabitants of urban and rural Shanghai.

The serum lipid levels (mean +/- SD) of 3312 healthy urban and rural inhabitants over 40 years of age in Shanghai were studied. The results were: cholesterol 166.7 +/- 30.9 mg/ml, triglyceride 81.1 +/- 42.3 mg/dl, HDL-cholesterol (HDLc) 57.4 +/- 11.6 mg/dl, HDL2c 20.6 +/- 9.8 mg/dl and HDL3c 37.1 +/- 7.8 mg/dl. Dietary surveys were carried out in 512 of these subjects and their average daily nutrient intake was estimated to be: total calories 2,577 Kcal, proteins 656 g (50.7 g of vegetable proteins), fat 69.1 g (P/S ratio 0.70), carbohydrates 423 g, cholesterol 282 mg, dietary fibres 23.5 g, sodium 4993 mg, potassium 2,618 mg and magnesium 575 mg. The serum lipid levels of urban and rural inhabitants were compared. Total cholesterol levels were significantly higher in urban inhabitants of all age groups and of both sexes, while triglyceride levels were significantly higher in urban inhabitants of certain age groups. However, HDLc levels, particularly HDL2c levels were significantly higher in rural inhabitants of most age groups and of both sexes. The above differences were probably the result of differences in dietary patterns and nutrient intake between urban and rural inhabitants.

Adult↗
PubMed1989

[Serial observation of human epidermal cell culture].

The primary and secondary cultures of human epidermal cells were observed serially with SEM and TEM. The cells interdigitated each other with numerous microvilli and creases on their surface. Mitoses could be seen in vigorous proliferating cells. However some cells showed degeneration and desquamation changes with less microvilli and relatively smooth surface. Once the cells became confluent, they began to stratify into basal, intermediate and upper layers or zones. The basal layer cells contained abundant organelles, free ribosomes and monofilaments with many desmosomes between the adjacent cells. The upper layer cells underwent terminal differentiation with fewer microvilli, sparse organelles even showed disorganization. As the culture time prolonged more cell showed this changes. The results here suggested that it is better to graft the confluent epidermal cell layer about three weeks after seeding as their proliferation is in good condition, and the basal cell layer should be applied onto the wound in favor of cell growth.

Cell Differentiation↗
PubMed1988

The design and synthesis of mimetics of peptide beta-turns.

The synthesis of an 11 membered ring bis-lactam, a system which is designed as a conformationally restricted mimetic of type I and type II beta-turns is described. Computer assisted molecular modeling was used to compare the predicted low energy conformers of the turn mimetic with idealized type I and type II turn structures. Initial computational analysis indicates that the basic ring structure will provide an excellent foundation for the development of a varieity of beta-turn mimetics.

Designer Drugs↗
PubMed1988

Late onset isofenphos neurotoxicity.

Late progressive polyneuropathy followed by pyramidal findings in a 20 year old agricultural labourer who ingested Isofenphos solution during his work, is presented. The patient was confined to a wheelchair within 6 weeks, regained walking ability within 6 months, and a 23 months' follow up revealed slight additional clinical improvement with minimal progression of the pyramidal signs. The neuropathic clinical manifestations, the EMG and the nerve conduction studies were compatible with a pathology of a distal, mainly axonal, mainly motor neuropathy.

Adult↗