Identification and characterization of growth hormone receptors in snakehead fish (Ophiocephalus argus cantor) liver

The specific binding of 125I-labeled fish growth hormone (GH) to hepatic membranes prepared from several freshwater fish was assessed. A high level of growth hormone receptor (GHR) was detected on the hepatic membranes of the snakehead fish (Ophiocephalus argus Cantor). Scatchard analysis of the binding data showed a single class of high affinity binding site with a binding affinity (Ka) of 1.45 +/- 0.23 x 10(9) M-1 and a binding capacity (Bmax) of 198 +/- 57 fmol/mg protein. The binding was specific for fish GH and was saturable. In addition, the specific binding was temperature- and time-dependent, reaching a steady state after 16 hr of incubation at 25 degrees . The molecular weight of GHR as measured by Sephadex G-200 column chromatography and Western blot analysis using a monoclonal antibody (Mab263) against GHR was found to be 200-400 and 90-93 kDa, respectively. Two bands at 65 and 89 kDa were identified in ligand crosslinking studies of membrane receptors. A sensitive teleost GH radioreceptor assay (RRA) was developed, using recombinant fish GH and a membrane preparation from snakehead fish liver, capable of measuring bioactive GH in fish sera or other samples.

Motor power pharmacodynamics of subarachnoid hyperbaric 5% lidocaine in the sitting position

BACKGROUND

Repetitive dynamometric measurement using a plantar flexion power device (PFPD) provides detailed data describing the onset and offset of motor block following spinal administration of lidocaine. The aim of this study was to evaluate administration of two doses of spinal lidocaine in the sitting position to determine whether our dynamometric model produces data consistent with our current understanding of the pharmacokinetics of subarachnoid, hyperbaric, 5% lidocaine.

METHODS

Twenty male patients (54 to 80 yr) undergoing cystoscopy received spinal anaesthesia with either 75 mg (n = 10) or 100 mg of hyperbaric lidocaine 5%, in the sitting position, under standardised conditions. Plantar flexion muscle power was recorded during onset and offset of anaesthesia using a load cell interfaced with a computer (PFPD).

RESULTS

Onset of paralysis following spinal block in the sitting position was rapid and complete with motor power declining exponentially to 5% of preoperative values by 8.5 min in all patients. There was no difference in decay or recovery of plantar flexion motor power data between dosage groups in the sitting position. Measurement using the PFPD shows that onset of motor paralysis is described by an exponential decay and that motor recovery occurs at a fixed rate. Extent of block to cold and pinprick was similar in both dosage groups in the sitting position (median T4).

CONCLUSION

This study shows that in the sitting position, doses less than 75 mg of 5% hyperbaric lidocaine are required to significantly improve ambulatory times.

Biomechanics of knee ligament healing, repair and reconstruction

Injuries of the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL) are common, accounting for 90% of all knee ligament injuries in young and active individuals. During the last decade, our research center has focused on MCL healing and ACL reconstruction. We have found that the MCL heals without intervention after an isolated injury, and that primary repair offers no apparent advantage. After a combined injury of the ACL and MCL, the ACL requires reconstruction, whereas primary repair again contributes little or nothing toward MCL healing. Midsubstance ACL injuries have limited healing ability. Hence, the treatment of choice for a torn ACL in a young, active patient is generally reconstruction with an autograft or allograft. However, the appropriate replacement graft and reconstruction technique to use are still debated. Current research efforts have been placed on investigating the magnitude and direction of in situ forces in the human ACL. We use a six-component universal force moment sensor combined with a six-degree-of-freedom (DOF) robotic manipulator to learn as well as to reproduce the six-DOF motion of the knee before and after ACL injury. This way, the in situ force in the ACL under an anterior posterior tibial load of 110 N was obtained. This methodology should make it possible to obtain the needed data to aid in better understanding of ACL reconstruction and possible development of improved clinical management.

Temperature-dependent ultraviolet resonance Raman spectroscopy of the premelting state of dA.dT DNA

Poly(dA).poly(dT) and DNA duplex with four or more adenine bases in a row exhibits a broad, solid-state structural premelting transition at about 35 degrees C. The low-temperature structure is correlated with the phenomena of "bent DNA." We have conducted temperature-dependent ultraviolet resonance Raman measurements of the structural transition using poly(dA).poly(dT) at physiological salt conditions, and are able to identify, between the high and low temperature limits, changes in the vibrational frequencies associated with the C4 carbonyl stretching mode in the thymine ring and the N6 scissors mode of the amine in the adenine ring of poly(dA).poly(dT). This work supports the model that the oligo-dA tracts' solid-state structural premelting transition is due to a set of cross-stand bifurcated hydrogen bonds between consecutive dA. dT pairs.

A preliminary study of C-reactive protein in the diagnosis and monitoring of Lyme disease

Concentrations of C-reactive protein (CRP) in the serum of 14 patients suffering from Lyme disease were measured. 86% of these patients were found to have abnormally high concentrations of serum CRP (range 14-158 mg/L). The CRP concentration of a 60-year-old patient abated from 29 mg/L to 13 mg/L after treatment. Results suggest that serum CRP concentration can provide a valuable and accurate means for the clinical diagnosis and monitoring of Lyme disease.

UNC-40, a C. elegans homolog of DCC (Deleted in Colorectal Cancer), is required in motile cells responding to UNC-6 netrin cues

UNC-6 netrin, a laminin-related protein secreted from neuroglia and neurons along the ventral midline, orients migrating cells and pioneering growth cones on the nematode epidermis. UNC-5, a cell surface protein expressed on motile cells and pioneer axons, orients movements away from UNC-6 sources. UNC-40, a homolog of the cell surface proteins DCC (Deleted in Colorectal Cancer) and neogenin, is also expressed on motile cells and pioneer neurons. UNC-40 acts cell autonomously to orient movement toward UNC-6 sources. For cells coexpressing UNC-5, it helps orient movement away from UNC-6 sources. Finally, UNC-40 helps determine the dorsoventral position of cells undergoing purely longitudinal migrations. Together with the recent report that DCC is a netrin receptor in vertebrates, our results suggest that UNC-40 is a component of UNC-6 receptors on motile cells.

Deleted in Colorectal Cancer (DCC) encodes a netrin receptor

The guidance of developing axons in the nervous system is mediated partly by diffusible chemoattractants secreted by axonal target cells. Netrins are chemoattractants for commissural axons in the vertebrate spinal cord, but the mechanisms through which they produce their effects are unknown. We show that Deleted in Colorectal Cancer (DCC), a transmembrane protein of the immunoglobulin superfamily, is expressed on spinal commissural axons and possesses netrin-1-binding activity. Moreover, an antibody to DCC selectively blocks the netrin-1-dependent outgrowth of commissural axons in vitro. These results indicate that DCC is a receptor or a component of a receptor that mediates the effects of netrin-1 on commissural axons, and they complement genetic evidence for interactions between DCC and netrin homologs in C. elegans and Drosophila.

[Cell cycle and apoptosis]

The progression of cell cycle in embryonic cells from oceanic bionts to mammalians is initiated, promoted and terminated under the regulation of cell cycle gene products, named cyclins, and a p34 (cdc 2). Besides, oncogene (proto-oncogene) products such as p53 and pRB also directly regulate the progression of cell cycle. However, the p34 (cdc 2) which promotes the mitotic cell division also initiates the apoptosis of certain cells. Therefore, mutations of genes that regulate the normal progression of cell cycle would cause cells in the cell cycle undergoing either apoptosis or uncontrollable proliferation.

Risk factors for falls in the Chinese elderly population

BACKGROUND

Besides being the major cause of hip fracture, falls also have important consequences in injuries and mortality, especially in the elderly population. This study investigated the occurrence of and the correlates of falls in a cohort of Hong Kong Chinese elderly aged 70 years and above.

METHODS

The research was based on the baseline cross-sectional study of an age- and sex-stratified cohort consisting of 1,947 ambulatory subjects. The occurrence of falls was based on the previous 12 months. Logistic regression analysis was used to test the effect of each independent variable, adjusting for age and sex. Multivariate logistic regression analysis based on the backward elimination procedure was used for the final model.

RESULTS

Previous white-collar employment, poor self-perceived health, dizziness, slow gait velocity, difficulties in activities of daily living, non-practice of "morning walk," body mass index in the range of 20-24, use of local skin preparation, and presence of cerebrovascular disease were independently associated with falls. Smokers were found to have an independent decreased risk of falls. Neither age nor sex was significantly associated with falls after adjusting for the other explanatory variables.

CONCLUSIONS

The results from this population-based cross-sectional study form a basis for further prospective study on falls in the Chinese elderly population. Both intrinsic and extrinsic factors including circumstances and consequences of falls are important considerations in the strategy for the prevention of falls.

Pulsed-field electrophoresis in microlithographic arrays

Transverse pulsed-field electrophoresis of DNA has been conducted in a silicon array engineered by optical lithography and the motion of individual molecules observed by fluorescence microscopy. In strong fields, the molecules can be maintained in highly stretched, linear conformations. When the field is switched through an obtuse angle, they head off in the new direction led by what was formerly their tail end. This backtracking gives rise to fractionation that is linear with molecular weight. A simple prescription exists for choosing the field parameters to obtain a particular range of separation. Since the molecular motions are much more uniform than those that occur in a gel, it is anticipated that the arrays will permit more efficient fractionation than traditional pulsed-field gel electrophoresis. Arrays suitably scaled down in size may be useful for pulsed-field sequencing.

Pharmacodynamics of subarachnoid hyperbaric 5% lignocaine

Twenty male patients (55 to 85 yr) undergoing cystoscopy received spinal anaesthesia with either 75 mg (n = 10) or 100 mg of hyperbaric lignocaine 5% under standardised conditions. Plantar flexion muscle power was recorded during onset and offset of anaesthesia using a load cell interfaced with a computer (PFPD) and these data were compared with intermittent clinical assessments of spinal anaesthesia. Onset of paralysis was rapid and complete with motor power declining exponentially to 5% of preoperative values by 5 minutes in all patients. Extent of block to cold and pinprick was similar in both dosage groups (median T4), as was the rate of block onset. Block regression was complete by three hours in all patients and restitution of plantar flexion motor power was associated with normal thermosensibility at L1 and recovery of the patient's ability to walk and micturate. Recovery of plantar flexion motor power occurred at 95.5 +/- 7.38 min in patients given 75 mg compared with 129 +/- 9.5 min in those given 100 mg lignocaine (P < 0.05). The time between onset and full motor recovery in the 75 mg group (7.2 +/- 1.2 min) was less than the 100 mg lignocaine group (29 +/- 5.1 min) (P < 0.001). The larger dose of lignocaine did not confer any clinical advantage in block onset or intensity and made the onset of recovery less predictable. The Bromage grading, while clinically appropriate during anaesthesia onset, does not provide data relating to the density of block and the PFPD was therefore useful for describing the anaesthesia recovery phase.

Effect of partial laceration on the structural properties of the canine FDP tendon: an in vitro study

The appropriate management of partially lacerated digital flexor tendons in zone 2 is controversial. Tenorrhaphy has been advocated by some on the basis of improving tendon gliding function, whereas others have recommended foregoing tenorrhaphy because of the negative impact of repair on the tensile strength of the tendon. In light of this division, we undertook a study of the effect of varying degrees of partial laceration on the structural properties of the canine flexor digitorum profundus tendon. Lacerations up to 90% of the tendon cross-sectional area were surgically fashioned. We conclude that the structural properties of the tendon are increasingly adversely affected as laceration size increases. However, based on previous estimates of in vivo forces, even tendons with up to 60% cross-sectional area involvement may be strong enough to withstand an early active mobilization regimen. Further, we conclude that neither calipers nor naked-eye estimates provide a reliable means of assessing the extent of tendon laceration.

Determinants of bone mass in the Chinese old-old population

One hundred and eighty-eight elderly men and women were included in a study of bone mass at the neck of femur and its related factors. The study subjects were a subsample of a Hong Kong wide study of the elderly population aged 70 years and above. The study variables included age, sex, body measurements of height, weight, body mass index, dietary calcium intake, grip strength, 16 feet (5 m) gait speed, smoking, drinking, and years since menopause among women. The neck of femur bone mineral density among elderly men was about 1 standard deviation higher than that of women. Subjects aged 85 years and above had about 20% lower bone mineral density at the neck of femur when compared with those in the age group 70-74 years. Mean dietary calcium intake ranged between 300 and 430 mg/day and was not associated with bone mass. Multiple regression analysis showed that body weight, 16 feet gait speed, sex and alcohol consumption explained 46% of the total variance of femoral neck bone mineral density. Body weight was the most significant predictor of bone mineral density, with a partial correlation coefficient of 0.5. The maintenance of body weight within the acceptable weight range and promotion of physical fitness may be important measures in reducing bone loss in the elderly population.

Determinants of serum 1,25-dihydroxyvitamin D concentration in healthy premenopausal subjects

Concentrations of serum phosphate and parathyroid hormone (PTH) are well known regulators of the production of 1,25-dihydroxyvitamin D (1,25-(OH)2D) and acidosis is known to affect the serum concentration of 1,25-(OH)2D. However, the factors that play a role in the regulation of serum 1,25-(OH)2D concentration in healthy subjects have not been fully evaluated. The associations of ionised calcium, pH, serum concentration of phosphate, PTH, 25-hydroxyvitamin D (25-OHD) and serum 1,25-(OH)2D were examined in 296 healthy premenopausal women (age range 17-40 years). Calculation of partial correlation coefficients showed that serum 1,25-(OH)2D was significantly correlated with phosphate (r = -0.148, P < 0.01), pH (r = 0.221, P < 0.001) and PTH (r = 0.136. P < 0.01). Ionised calcium was not related to serum 1,25-(OH)2D. When the results were stratified according to quartiles based on serum 1,25-(OH)2D concentration, significant trends (by analysis of variance) were seen in phosphate, pH, age, albumin and 25-OHD. Stepwise multiple regression analysis showed that phosphate and pH were the major contributors of serum 1,25-(OH)2D levels. There was a small contribution from PTH and 25-OHD. The results suggest that in young healthy premenopausal women plasma phosphate and pH may be important determinants of serum 1,25-(OH)2D concentration.

Determinants of bone mass in Chinese women aged 21-40 years. II. Pattern of dietary calcium intake and association with bone mineral density

A study on the determinants of bone mass in young women is being carried out among 287 young Chinese women aged 21-40 years. The baseline cross-sectional data show that the mean dietary calcium intake, estimated from the quantitative food frequency method, was 448 mg/day (standard deviation = 219). About 50% of the calcium source was from vegetables and 22% from dairy products. Among women aged 21-30 years, those with a dietary calcium intake of at least 600 mg/day had a 4%-7% higher mean bone mineral density at the spine and femur when compared with those with a mean intake below 300 mg/day. In women aged 31-40 years, subjects belonging to the highest quartile of calcium density (> or = 35 mg/420 kJ) had a 3%-8% higher mean bone mineral density at the spine and femur when compared with those in the lowest quartile (< 20.8 mg/420 kJ). Favorable calcium intake is beneficial in this population of young women with habitual low dietary calcium intake.

Thermodynamics and premelting conformational changes of phased (dA)5 tracts

Using synthetic 45 bp long DNAs of known sequences, we have studied (i) the unusual structure that the phased A-tracts have at temperatures below 37 degrees C, (ii) the thermodynamics of the loss of that aberrant structure well below the duplex melting temperature, and (iii) the conformational changes that occur with temperature. Using temperature-dependent circular dichroism, we detect a low-temperature structural transition in a 45-mer duplex with four segments of phased (dA)5 tracks separated by five segments of five randomized G-C pairs, but none in the corresponding isomeric random sequence 45-mer duplex. Differential scanning calorimetry measurements reveal the enthalpy of this preglobal melting transition to be 3.5 kcal/mol.AT pair or 4.4 kcal/mol.AA step. The integrated enthalpy change for this helix-to-helix intramolecular event only is about 16% of the global duplex-to-single-strands melting enthalpy and is relatively broad compared to the global melting event (about 30 vs 15 degrees C for the full width at half maxima). Electric birefringence decay measurements show that the phased 45 bp duplex has a rotational time constant of 100 ns at 5 degrees C which increases to 220 ns above 40 degrees C. Simple modeling of the dynamics within the junction model for bending yields that the bend per A-tract is 42 degrees at 5 degrees C, decreasing to 0 degrees above 40 degrees C. We suggest that this sequence-dependent structure which "melts" at physiological temperatures may be relevant to DNA topology and function.

A longitudinal study of the determinants of bone mass in Chinese women aged 21 to 40. I. Baseline association of anthropometric measurements with bone mineral density

The bone mineral density of the lumbar spine (L2 to L4) and neck of the femur of 293 Chinese women aged 21 to 40 years was measured using a dual x-ray densitometer. The participants were recruited from subjects registered with the University Family Medicine Clinic in Hong Kong. Our cross-sectional data showed that maximal bone mass occurs in the early 30s. Both the spine and hip bone masses were observed to decline at a rate of around 1% per annum from the early 30s onward. Body weight, lean body mass, and body fatness were significantly associated with the mineral density of the spinal and femoral bones after or around the attainment of peak bone mass, while no correlation of these data was observed in the younger age group (20 to 28 years). Other factors may play a more important role than body mass in influencing bone mineral density before attainment of peak bone mass.

Physical studies of DNA premelting equilibria in duplexes with and without homo dA.dT tracts: correlations with DNA bending

We have employed a variety of physical methods to study the equilibrium melting and temperature-dependent conformational dynamics of dA.dT tracts in fractionated synthetic DNA polymers and in well-defined fragments of kinetoplast DNA (kDNA). Using circular dichroism (CD), we have detected a temperature-dependent, "premelting" event in poly(dA).poly(dT) which exhibits a midpoint near 37 degrees C. Significantly, we also detect this CD "premelting" behavior in a fragment of kDNA. By contrast, we do not observe this "premelting" behavior in the temperature-dependent CD spectra of poly[d(AT)].poly[d(AT)], poly(dG).poly(dC), poly[d(GC)].poly[d(GC)], or calf thymus DNA. Thus, poly(dA).poly(dT) and kDNA exhibit a common CD-detected "premelting" event which is absent in the other duplex systems studied in this work. Furthermore, we find that the anomalous electrophoretic retardation of the kDNA fragments we have investigated disappears at temperatures above approximately 37 degrees C. We also observe that the rotational dynamics of poly(dA).poly(dT) and kDNA as assessed by singlet depletion anisotropy decay (SDAD) and electric birefringence decay (EBD) also display a discontinuity near 37 degrees C, which is not observed for the other duplex systems studied. Thus, in the aggregate, our static and dynamic measurements suggest that the homo dA.dT sequence element [common to both poly(dA).poly(dT) and kDNA] is capable of a temperature-dependent equilibrium between at least two helical states in a temperature range well below that required to induce global melting of the host duplex. We suggest that this "preglobal" melting event may correspond to the thermally induced "disruption" of "bent" DNA.

Adenoid cystic carcinoma of prostate. Report of a case

A case of adenoid-cystic carcinoma of the prostate is presented. The differential diagnosis and a brief discussion of the possible histogenesis is presented.

Peer review using a paired-comparison technique

A paired-comparison technique is used to enable surgical residents and attending surgeons to make peer judgments of each other. Comparative peer judgments were made in three areas: the ability of the surgeon to make a diagnosis and to decide on a plan of active medical care, the operating ability of the surgeon, and the postoperative care of the patient. This method of peer judgment ensures the confidentiality of those making the judgments, and the analysis results in a final ranking of the surgeons and surgical residents with indicated significant differences (P less than 0.05) among them. The technique also includes an assessment of how consistent each judge is in making comparisons of fellow surgeons.

Rotational diffusion of cell surface components by time-resolved phosphorescence anisotropy

The rotational diffusion of concanavalin A receptors of viable Friend erythroleukemia cells and the band 3 anion transport system of human erythrocytes has been measured via the time-dependent phosphorescence emission intensity and anisotropy of triplet probes excited by a 5-ns laser pulse. High-quality phosphorescence decay curves with a 10-microseconds time resolution were obtained at concentrations of the eosin probe down to 20 nM and in aqueous media at temperatures of 4-38 degrees C. A strong temperature dependence in the rotational behavior was observed for the band 3 anion transport protein, but the lectin receptors of the Friend erythroleukemia cells were found to be immobile on the time scale of 1-4000 microseconds at either 4 degrees C or 37 degrees C. The technique is applicable to other triplet probes and membrane components of living cells under conditions that do not destroy viability.

Proximity of lectin receptors on the cell surface measured by fluorescence energy transfer in a flow system

Molecules of the lectin concanavalin A have been labeled separately with the fluorescein and rhodamine chromophores and jointly bound to the surface of transformed Friend erythroleukemia cells. The two dyes constitute an ideal donor-acceptor pair for fluorescence resonance energy transfer thereby permitting the determination of the proximity relationships between bound ligand molecules and the corresponding surface receptors. The transfer efficiency at saturation (about 57%) was measured in a multiparameter flow system using laser excitation at 488 nm and detection of fluorescein and rhodamine emission intensities as well as the emission anisotropy of the rhodamine fluorescence for each cell. The degree of energy transfer was estimated from the quenching of donor emission, the sensitization of acceptor emission, and the depolarization of acceptor fluorescence. The system has been modeled according to a formalism developed by Gennis and Cantor (Biochemistry 11: 2509, 1972). We estimate the separation between the surfaces of bound lectin molecules at saturation to be 0-40 A, a range possibly characteristic for micropatches induced by ligand binding.