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Biomedical subjects

J Luo

Publications and source records attributed to J Luo.

At least 379 records · Page 21Linked to original sources
PubMed1991

Relative effects of flow-resistive and pressure-biased respiratory loading.

The effects of pressure-biased breathing (PBB), which simulates positive pressure respirator use, were studied in 15 volunteer subjects during laboratory exercise. PBB was compared with inspiratory resistance: dead space (ID) load and a no-load (N) situation. PBB had adverse subjective effects comparable with those of ID. Physiologically, PBB led to a small decrease in inspiratory time and an increase in expiratory time as well as an increase in the intensity of ventilatory effort as measured by the mean inspiratory flow rate. It is postulated, based on these findings, that PBB has significant effects on the resting lung volume, leading to both physiologic and subjective consequences.

Adult↗
PubMed1990

A two-dimensional analog VLSI circuit for detecting discontinuities in early vision.

A large number of computer vision algorithms for finding intensity edges, computing motion, depth, and color, and recovering the three-dimensional shape of objects have been developed within the framework of minimizing an associated "energy" or "cost" functional. Particularly successful has been the introduction of binary variables coding for discontinuities in intensity, optical flow field, depth, and other variables, allowing image segmentation to occur in these modalities. The associated nonconvex variational functionals can be mapped onto analog, resistive networks, such that the stationary voltage distribution in the network corresponds to a minimum of the functional. The performance of an experimental analog very-large-scale integration (VLSI) circuit implementing the nonlinear resistive network for the problem of two-dimensional surface interpolation in the presence of discontinuities is demonstrated; this circuit is implemented in complementary metal oxide semiconductor technology.

Algorithms↗
PubMed1990

Decarboxylation of uroporphyrinogen III by erythrocyte uroporphyrinogen decarboxylase. Evidence for a random decarboxylation mechanism.

The isomeric composition of type-III heptacarboxylic porphyrinogens derived from decarbosylation of uroporphyrinogen III by erythrocyte uroporphyringogen decarboxylase was analysed by h.p.l.c. with electrochemical detection. All four possible isomers were identified, and there were little differences in the proportion of isomers formed by erythrocytes from normal subjects and from patients with sporadic porphyria cutanea tarda. The results provide conclusive evidence that the normal decarboxylation pathway is random in nature, and the fourth isomer only increases when enzyme abnormality is found.

Carboxy-Lyases↗
PubMed1990

Purine nucleotides and AMP deamination during maximal and endurance swimming exercise in heart and skeletal muscle of rats.

The purine nucleotides, phosphocreatine (PCr), ammonia, and lactic acid were investigated in skeletal muscles of rats with prominent type I, type IIa, type IIb fibers, and the heart after exhaustive and endurance swimming tests. ATP, ADP, AMP, IMP, and PCr were determined by HPLC with UV detection in controls after maximal and endurance training for 6 weeks with or without a respective final test and also after final exhaustive or endurance test without preceding training. The swimming time in these tests was longer with than without training. A pronounced ATP decrease and a large increase in IMP, up to 4.9 mumol/g wet weight, were found in type IIb fibers after the maximal final test without preceding training. Compared with skeletal muscle, the IMP concentration in the heart was significantly lower after all exercise bouts, even though after maximal exercise AMP augmentation was highest, ATP reduction was greatest, and energy charge was lowest. The difference between the heart and skeletal muscle in the production of IMP indicates that despite AMP and ADP accumulation, myoadenylate deaminase (MAD) activity in the heart is considerably lower than in skeletal muscle, especially in type IIb fibers. The smaller amount of MAD per tissue, and also the different MAD isozyme pattern of the heart as reported in the literature, may be attributed to lower activation. The difference between MAD activation of the soleus muscle and of the iliacus muscle, both consisting predominantly of type I fibers, suggests that MAD activity may be influenced by biochemical demand and oxygen supply, varying with the anatomical localization. Even though ammonia and lactic acid were highly correlated, it is questionable whether the H+ ion increase due to the lactate accumulation itself triggers MAD activation, as has been found for AMP and ADP in skeletal muscle.

AMP Deaminase↗
PubMed1990

In search of a Hoogsteen base paired DNA duplex in aqueous solution.

When the oligodeoxynucleotides d(A)6 and d(T)6 are mixed together in a 1:1 ratio (in 100 mM NaCl), the NH signals in the NMR spectrum gave a typical signature of Watson-Crick paired (WC) and Hoogsteen paired (H) AT base pairs. The observation indicates two schemes: Scheme I, WC and H duplexes in slow equilibrium, i.e., WC in equilibrium with H, Scheme II, the WC helix formed is unstable and that it disproportionates into a triple helix (TR) and free d(A)6. We show that (i) addition of extra d(A)6 does not change the helix composition, (ii) addition of a minor-groove specific drug Dst2 (a distamycin analogue) results in an exclusive WC helix-drug duplex, while it does not destabilize triple helix in a 1:2 mixture. In addition we have compared the melting profile, 31P NMR spectra, 1H NMR spectra and the salt dependence of the 1:1 mixture and that of a pure triple helix. All the data from the above experiments overwhelmingly favor Scheme I. However Scheme II cannot be categorically excluded. Based on 1D/2D NMR studies, we have characterized the structural properties of the Hoogsteen double helix in terms of nucleotide conformations. In addition, we computationally demonstrate that the relative stability of the WC over the H duplexes increases with increasing chain length.

Adenine↗
PubMed1990

Dexamethasone increases hepatic insulin-like growth factor binding protein-1 (IGFBP-1) mRNA and serum IGFBP-1 concentrations in the rat.

Glucocorticoid excess is associated with growth retardation in both man and experimental animals. We have previously reported that dexamethasone (DXM) inhibits growth hormone induction of insulin-like growth factor-I (IGF-I) mRNA in the hypophysectomized rat and reduces steady-state IGF-I mRNA levels in the intact rat. However, in these experiments, DXM had surprisingly little effect on serum IGF-I concentrations. Here, we have examined the effect of DXM on hepatic insulin-like growth factor binding protein-1 (IGFBP-1) mRNA levels and on serum IGFBP-1 concentrations. After a single ip injection of DXM, 6 micrograms/100 g body wt, IGFBP-1 mRNA increased 2.24 +/- 0.25-fold, P less than 0.05 at 1 h and declined to normal levels in 6-12 h. A dose-dependent increase in increased hepatic IGFBP-1 mRNA abundance was seen in rats killed 1 h after an ip injection of DXM, 0.1 to 60 micrograms/100g body wt. As little as 1 microgram/100g body wt, significantly enhanced hepatic IGFBP-1 mRNA levels; 2.02- +/- 0.38-fold, P less than 0.05. This effect appeared to be post-transcriptional, since IGFBP-1 transcription in hepatic nuclei from rats treated with DXM was not significantly different from untreated rats. When DXM, 1 microgram/rat, was administered daily for 6 days a significant increase in IGFBP-1 mRNA was detected; 2.02 +/- 0.39-fold, P less than 0.05. A more marked increase was seen with 6 and 60 micrograms/rat of DXM; 4.47 +/- 1.08- and 10.61 +/- 0.31-fold, respectively. Serum was analyzed by sodium dodecyl sulfate-plyacrylamide gel electrophoresis and immunoblotting using antisera raised against a synthetic peptide derived from the predicted sequence of rat IGFBP-1. The antisera recognized a doublet of approximately 30 kDa. A dose-dependent increase in the abundance of these BPs were seen in the serum from rats treated chronically with DXM. The observations reported here clearly demonstrate that DXM increases hepatic IGFBP-1 mRNA and serum IGFBP-1 concentrations. If IGFBP-1 functions to decrease the bioavailability of IGF-1 in vivo the enhanced expression of IGFBP-1 may be an additional mechanism whereby glucocorticoid excess results in growth retardation.

Animals↗
PubMed1990

[Effects of high carbohydrate and high fat diet on plasma apolipoproteins AI, AII, B100, CI, CII, CIII and E in normal and hypertriglyceridemic humans].

Effects of high carbohydrate (CHO) and high fat diet on plasma apolipoproteins (apo) AI, AII, B100, CI, CII, CIII and E were assessed in 10 healthy subjects and 10 patients with endogenous hypertriglyceridemia. High CHO diet consisted of 80% CHO, 5% fat and 15% protein of total calories, and high fat diet consisted of 40% CHO, 45% fat and 15% protein. After 5 days normal diet (60% of total calories from CHO, 25% from from fat and 15% from protein), the subjects studied received sequentially high CHO diet and normal diet for 5 days and high fat diet and normal diet for 5 days. Fasting blood samples were drawn on days 1, 3, and 5 of high CHO and high fat diet period, and 5 days after taking normal diet. Results showed that fasting plasma apo AI slightly decreased (P less than 0.01) on day 3 of the high CHO diet period and slightly increased (P less than 0.01) on day 3 of the high fat diet period, plasma apo AII increased after intake of high CHO diet, but no changes were observed after the subjects were placed on high fat diet. Fasting plasma apo B100 decreased (P less than 0.001) in hypertriglyceridemics on the 3rd day of the high CHO diet, but no differences were noted in normal subjects on the same diet. On the 3rd day of the high fat diet period, apo B100 increased (P less than 0.01) in normal subjects, but no changes were found in hypertriglyceridemics. Apo CII and CIII levels declined during the high CHO diet period but increased in normal subjects after intake of high fat died.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Quantification of human serum apolipoprotein A II by radial immunodiffusion].

A radial immunodiffusion assay (RID) for human serum apolipoprotein A II (apo A II) was developed. Antisera to human apoA II were raised in goats with purified apoA II. The antibody-gel plate was prepared with 1% agarose. 5 microliters of each sample was added in a well. Diffusion was performed at 25 degrees C for 48 h. The minimum measurable concentration of apoA II was 58ng. The standard curve with a working range of 17.3-69 mg/dl was plotted. The coefficients of variation of within and between plates were 1.5-4.6% and 5.6% respectively. The recovery of the assay was 90.3-102.0%. The concentrations of apoA II for healthy men and women in Chengdu area were 26.7 +/- 4.4 mg/dl (n = 45) and 26.6 +/- 4.6 mg/dl (n = 31) respectively.

Apolipoprotein A-II↗
PubMed1990

Does paramedic-base hospital contact result in beneficial deviations from standard prehospital protocols?

We reviewed written and audio records of paramedic-base hospital radio contact to determine whether care differed from that suggested in standard prehospital care protocols. Records of all 659 contacts for seizure, syncope, abdominal pain, or altered mental state during 1987 (28.4% of all contacts) were scored for the use of standard therapies (such as intravenous access, oxygen, naloxone hydrochloride) and unanticipated therapies (intubation, nitroglycerin). Cases that involved unanticipated treatments were reviewed to determine whether they could have been prospectively identified by simple clinical findings. Standard therapies were used in the majority of patients. Unanticipated therapies were administered to 13 patients, all of whom had abnormal vital signs, diaphoresis, respiratory distress, or a second prominent symptom. Data suggest that protocols could replace radio contact for most patients and that the few who might benefit from radio contact can be easily identified. A 90% reduction in radio contacts in Los Angeles county could save $3 million each year.

Abdominal Pain↗
PubMed1990

Effect of three-year multidrug therapy in multibacillary leprosy patients.

The feasibility and effects of a 3-year treatment using rifampicin (RFP), clofazimine (B663) and dapsone (DDS) in multibacillary leprosy patients in Yangzhou Prefecture and Dongtai County (1983-1986) are reported. Among 591 active multibacillary leprosy patients in the two areas, 569 (96.30%) were treated with this regimen. Of 303 cases available for analysis, 196 (64.7%) cases showed negative skin smears and clinical inactivity. The rest showed different degrees of improvement. The average reduction of BI was 0.78. The intensity and frequency of ENL and neuritis decreased markedly with treatment. The main side-effects were pigmentation and ichthyosiform changes of the skin, but these did not influence treatment.

Adult↗
PubMed1990

[15 years' observation and related research on diagnosis and treatment according to traditional Chinese medicine of elevated serum lipids in 54 cases of coronary disease].

The increasing rate of cholesterol (CH) of 54 cases with coronary heart disease was 33.33%. According to CH level, the authors divided them into two groups: the normal one (I) and the high one (II). By fifteen-year observation, CH of Group I kept normal, only with its triglyceride (TG) a little higher than ordinary level. But the CH and TG of Group II, which had been treated with anticholesteremic drugs, was obviously higher than Group I (P less than 0.05). In connection with identification according to TCM, both CH and TG of deficiency of Yang, and deficiency of both Yin and Yang were higher, especially TG (P less than 0.01). TG of the type of blood stasis was higher (P less than 0.01) except anticholesteremic drugs for Group II. The two groups were treated with the same combined treatment of TCM and WM. The long term effect of fifteen years in Group I was more obvious than in Group II. This showed that the treatment of high serum lipid of CHD was more difficult.

Adult↗
PubMed1989

The effect of acute and chronic insulin administration on insulin-like growth factor-I expression in the pituitary-intact and hypophysectomised rat.

Although growth hormone is known to be the main regulator of insulin-like growth factor-I, insulin has also been shown to play a role in regulating serum insulin-like growth factor I levels in diabetic animals. While this effect is thought to be due to correction of metabolic perturbations, some studies have suggest that insulin may have a direct effect on growth and/or insulin-like growth factor-I levels. We have examined the effects of acute and chronic insulin administration to non-diabetic, pituitary-intact and hypophysectomised rats. Rats were injected intraperitoneally with insulin as an acute bolus (10 U) or a chronic subcutanious infusion (low dose; 2.4 U/day, high dose; 12 U/day) over 5 days. Insulin-like growth factor-I mRNA was quantitated by Northern and slot blots of RNA from various tissues. A small (less than 2-fold) but significant increase (p less than 0.05) was seen in hepatic insulin-like growth factor-I mRNA abundance in pituitary-intact rats following acute insulin injection and chronic low dose insulin infusion. An increase in insulin-like growth factor-I mRNA levels was also seen in other tissues including diaphragm, lung, kidney and heart. A significant increase (p less than 0.05) in serum insulin-like growth factor-I levels was also observed 6 h after insulin injection. In contrast, in pituitary-intact rats which received high dose insulin infusion and were hypoglycaemic at the time of death, tissue levels of insulin-like growth factor-I mRNA were reduced compared to saline-treated control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Algorithm use in the treatment of pre-hospital ventricular fibrillation: an analysis of 160 cases.

In a series of 160 consecutive patients with pre-hospital ventricular fibrillation, outcomes were improved if base-station personnel precisely followed the initial 7 steps of standard VF algorithms. This improvement reached statistical significance regarding survival to hospital discharge (17% vs. 6%, P less than 0.05), and reflected a very strong trend with regard to initial resuscitation and admission to hospital (31% vs. 18%, 0.05 less than P less than 0.10). These measures of outcome were even more strongly related to field time, such that patients treated in the field for less than 15 min did far better than patients treated longer. While concordance with algorithms did not independently diminish field time in this study, this probably reflects the fact that paramedics had to establish base hospital contact and receive orders from base personnel in all patients; thus it is probable that allowing paramedics to treat patients in VF, using precise protocols, without prior communication with a base hospital, would diminish field time, and this might lead to even further improvement in patient outcome.

Adult↗
PubMed1988

DNA stem-loop structures in oligopurine-oligopyrimidine triplexes.

Closed circular DNA containing polypurine-polypyrimidine sequences can adopt a triple helical stem-loop structure under supercoiling pressure. We describe an automated procedure for building model loops and its application to the investigation of the polypyrimidine loop at the end of such a triple helical stem. All possible combinations of 3'-stacked and 5'-stacked structures have been examined for loops containing three, four, five, and six nucleotides. The lowest energy conformation is a four-membered loop with all bases stacked on the strand at the 3' end of the loop. The model predicts that sequences (GA)n, (GGGA)n and (GAAA)n should form the stem-loop structure more easily than (GGA)n and (GAA)n. It is also predicted that when a polypurine-polypyrimidine sequence converts from a double stranded structure to a triple stranded stem-loop, the most favorable conditions are those where an even number of basepairs makes the transition. Experimental tests of these predictions are also described.

DNA↗
PubMed1988

Vasectomy and health: cardiovascular and other diseases following vasectomy in Sichuan province, People's Republic of China.

The long-term sequelae of vasectomy were studied in a retrospective cohort study of 4596 vasectomized and 4340 nonvasectomized farmers from eight rural communes in Sichuan, People's Republic of China. The mean duration since the operation was 14.5 years with a range of 10 to 25 years. At the time of evaluation the vasectomized men were generally healthier than the non-vasectomized for a wide range of health indicators including clinical signs of cardiovascular disease, resting ECG changes, positive ECG changes following a maximal stress test, or fundus abnormalities. The lack of association between vasectomy and cardiovascular disease noted in Europe and the USA is supported by the present study conducted in a population with a low prevalence of cardiovascular disease and risk factors.

Adult↗