A family of mammalian Na+-dependent L-ascorbic acid transporters

Vitamin C (L-ascorbic acid) is essential for many enzymatic reactions, in which it serves to maintain prosthetic metal ions in their reduced forms (for example, Fe2+, Cu+), and for scavenging free radicals in order to protect tissues from oxidative damage. The facilitative sugar transporters of the GLUT type can transport the oxidized form of the vitamin, dehydroascorbic acid, but these transporters are unlikely to allow significant physiological amounts of vitamin C to be taken up in the presence of normal glucose concentrations, because the vitamin is present in plasma essentially only in its reduced form. Here we describe the isolation of two L-ascorbic acid transporters, SVCT1 and SVCT2, from rat complementary DNA libraries, as the first step in investigating the importance of L-ascorbic acid transport in regulating the supply and metabolism of vitamin C. We find that SVCT1 and SVCT2 each mediate concentrative, high-affinity L-ascorbic acid transport that is stereospecific and is driven by the Na+ electrochemical gradient. Despite their close sequence homology and similar functions, the two isoforms of the transporter are discretely distributed: SVCT1 is mainly confined to epithelial systems (intestine, kidney, liver), whereas SVCT2 serves a host of metabolically active cells and specialized tissues in the brain, eye and other organs.

Molecular and functional analysis of SDCT2, a novel rat sodium-dependent dicarboxylate transporter

Kidney proximal tubule cells take up Krebs cycle intermediates for metabolic purposes and for secretion of organic anions through dicarboxylate/organic anion exchange. Alteration in reabsorption of citrate is closely related to renal stone formation. The presence of distinct types of sodium-coupled dicarboxylate transporters has been postulated on either side of the polarized epithelial membrane in the kidney proximal tubule. Using a PCR-based approach, we isolated a novel member of the sodium-dependent dicarboxylate/sulfate transporter called SDCT2. SDCT2 is a 600-amino acid residue protein that has 47-48% amino acid identity to SDCT1 and NaDC-1, previously identified in kidney and intestine. Northern analysis gave a single band of 3.3 kb for SDCT2 in kidney, liver, and brain. In situ hybridization revealed that SDCT2 is prominently expressed in kidney proximal tubule S3 segments and in perivenous hepatocytes, consistent with the sites of high-affinity dicarboxylate transport identified based on vesicle studies. A signal was also detected in the meningeal layers of the brain. SDCT2 expressed in Xenopus oocytes mediated sodium-dependent transport of di- and tricarboxylates with substrate preference for succinate rather than citrate, but excluding monocarboxylates. SDCT2, unlike SDCT1, displayed a unique pH dependence for succinate transport (optimal pH 7.5-8.5) and showed a high affinity for dimethylsuccinate, two features characteristic of basolateral transport. These data help to interpret the mechanisms of renal citrate transport, their alteration in pathophysiological conditions, and their role in the elimination of organic anions and therapeutic drugs.

Minimally invasive surgical closure of atrial septal defects via a right anterior thoracotomy

BACKGROUND

Surgical closure of the atrial septal defect (ASD) is a low-risk operation with little post-operative morbidity involved. The standard approach to ASD closure is via a median sternotomy. However the post-operative midline scar is cosmetically undesirable.

PATIENTS

We report our experience with four female patients who have undergone closure of ASD through a right anterior thoracotomy and a left groin incision for femoral cannulation.

RESULTS

Post-operative recovery was uneventful. The cosmetic results of their operations were good.

CONCLUSION

Closure of ASD via a right anterior approach is a safe method and should preferably be used in young female patients, as better cosmetic results are expected.

Stoichiometry and kinetics of the high-affinity H+-coupled peptide transporter PepT2

Proton-coupled peptide transporters mediate the absorption of a large variety of di- and tripeptides as well as peptide-like pharmacologically active compounds. We report a kinetic analysis of the rat kidney high-affinity peptide transporter PepT2 expressed in Xenopus oocytes. By use of simultaneous radioactive uptake and current measurements under voltage-clamp condition, the charge to substrate uptake ratio was found to be close to 2 for both D-Phe-L-Ala and D-Phe-L-Glu, indicating that the H+:substrate stoichiometry is 2:1 and 3:1 for neutral and anionic dipeptides, respectively. The higher stoichiometry for anionic peptides suggests that they are transported in the protonated form. For D-Phe-L-Lys, the charge:uptake ratio averaged 2.4 from pooled experiments, suggesting that Phe-Lys crosses the membrane via PepT2 either in its deprotonated (neutral) or its positively charged form, averaging a H+:Phe-Lys stoichiometry of 1.4:1. These findings led to the overall conclusion that PepT2 couples transport of one peptide molecule to two H+. This is in contrast to the low-affinity transporter PepT1 that couples transport of one peptide to one H+. Quinapril inhibited PepT2-mediated currents in presence or in absence of external substrates. Oocytes expressing PepT2 exhibited quinapril-sensitive outward currents. In the absence of external substrate, a quinapril-sensitive proton inward current (proton leak) was also observed which, together with the observed pH-dependent PepT2-specific presteady-state currents (Ipss), indicates that at least one H+ binds to the transporter prior to substrate. PepT2 exhibited Ipss in response to hyperpolarization at pH 6.5-8.0. However, contrary to previous observations on various transporters, 1) no significant currents were observed corresponding to voltage jumps returning from hyperpolarization, and 2) at reduced extracellular pH, no significant Ipss were observed in either direction. Together with observed lower substrate affinities and decreased PepT2-mediated currents at hyperpolarized Vm, our data are consistent with the concept that hyperpolarization exerts inactivation effects on the transporter which are enhanced by low pH. Our studies revealed distinct properties of PepT2, compared with PepT1 and other ion-coupled transporters.

Characterization of a rat Na+-dicarboxylate cotransporter

The metabolism of Krebs cycle intermediates is of fundamental importance for eukaryotic cells. In the kidney, these intermediates are transported actively into epithelial cells. Because citrate is a potent inhibitor for calcium stone formation, excessive uptake results in nephrolithiasis due to hypocitraturia. We report the cloning and characterization of a rat kidney dicarboxylate transporter (SDCT1). In situ hybridization revealed that SDCT1 mRNA is localized in S3 segments of kidney proximal tubules and in enterocytes lining the intestinal villi. Signals were also detected in lung bronchioli, the epididymis, and liver. When expressed in Xenopus oocytes, SDCT1 mediated electrogenic, sodium-dependent transport of most Krebs cycle intermediates (Km = 20-60 microM), including citrate, succinate, alpha-ketoglutarate, and oxaloacetate. Of note, the acidic amino acids L- and D-glutamate and aspartate were also transported, although with lower affinity (Km = 2-18 mM). Transport of citrate was pH-sensitive. At pH 7.5, the Km for citrate was high (0.64 mM), whereas at pH 5.5, the Km was low (57 microM). This is consistent with the concept that the -2 form of citrate is the transported species. In addition, maximal currents at pH 5.5 were 70% higher than those at pH 7.5, and our data show that the -3 form acts as a competitive inhibitor. Simultaneous measurements of substrate-evoked currents and tracer uptakes under voltage-clamp condition, as well as a thermodynamic approach, gave a Na+ to citrate or a Na+ to succinate stoichiometry of 3 to 1. SDCT1-mediated currents were inhibited by phloretin. This plant glycoside also inhibited the SDCT1-specific sodium leak in the absence of substrate, indicating that at least one Na+ binds to the transporter before the substrate. The data presented provide new insights into the biophysical characteristics and physiological implications of a cloned dicarboxylate transporter.

Molecular genetics of cystinuria: mutation analysis of SLC3A1 and evidence for another gene in type I (silent) phenotype

BACKGROUND

Cystinuria is a hereditary disorder that affects luminal transport of cystine and dibasic amino acids in kidney and small intestine. Three subtypes have been defined on the basis of urinary excretion of cystine in obligate heterozygotes. Mutations in the SLC3A1 gene have been associated with the Type I phenotype.

METHODS

We investigated 20 cystinuria patients from Quebec (8 Type I/I, 9 Type I/III and 3 Type II/N) for mutations in SLC3A1. DNA was studied by Southern blotting and by the single strand conformation polymorphism (SSCP) protocol to identify mutations. Expression of mutations in Xenopus oocytes was performed to confirm the effect of missense mutations on cystine uptake.

RESULTS

Six novel mutations (2 large deletions, a 2 bp deletion and 3 single bp substitutions) were identified on the Type I allele. Four missense mutations (T216M, S217R, R270L and I618M) were expressed in vitro; the first three changes significantly decreased uptake.

CONCLUSIONS

Combined with our previous work, we have identified 15/16 mutations in SLC3A1 on Type I alleles in the eight Type I/I patients, but only one SLC3A1 mutation on the nine Type I alleles of the Type I/III patients. Therefore, we propose that the Type I phenotype could be caused by mutations in other, as yet unidentified cystinuria genes.

Differential in vivo activities of bovine growth hormone analogues

In rodents, bovine (b) growth hormone (GH) binds only to GH receptors, while human (h) GH binds to both GH and PRL receptors. The phenotypic consequences of expression of bGH and hGH in transgenic mice are different and, in some cases, opposite. In the present study, site-directed in vitro mutagenesis of the bGH gene was used systematically to eliminate its differences from hGH at one, two, three or four suspected of conferring lactogenic activity: D11, H18, S57 and T60, respectively (corresponding to sites 12, 19, 57 and 60 of the bGH molecule). The resulting bGH analogues were expressed in cell lines and in transgenic mice. All of the seven bGH analogues produced retained their ability to bind to GH receptors and exhibited somatogenic activity in vitro and in vivo. However, none of them were able to bind to PRL receptors or to elicit detectable lactogenic response in vitro. Transgenic animals expressing any of the generated analogues were characterized by gigantism and splanchnomegaly. The effects of expression of each of the double, triple or quadruple mutants on the seminal vesicle weight resembled the effects of wild-type hGH and differed from the effects of expression of wild-type bGH. There were differences between the effects of the expression of different bGH analogues on plasma PRL levels and on the PRL response to pharmacological blockade of catecholamine synthesis. Plasma LH levels in ovariectomized females were suppressed by several of the analogues tested, an effect not seen in animals expressing wild-type bGH or hGH. Dopamine turnover in the median eminence of male mice was also altered in animals expressing different bGH analogues but not in those expressing wild-type bGH or hGH. In ovariectomized females, the effects of different bGH analogs on the turnover of dopamine and norepinephrine in the median eminence included changes resembling those detected in animals expressing hGH, as well as alterations differing from the effects of both bGH and hGH. The results indicate that biological actions of these bGH analogues cannot be characterized simply in terms of enhanced or reduced somatogenic or lactogenic activity and raise a possibility that different sites, domains or features of tri-dimensional structure of GH are involved in its actions on different cellular targets.

Sodium leak pathway and substrate binding order in the Na+-glucose cotransporter

The Na+-glucose cotransporter (SGLT1) expressed in Xenopus laevis oocytes was shown to generate a phlorizin-sensitive sodium leak in the absence of sugars. Using the current model for SGLT1, where the sodium leak was presumed to occur after two sodium ions are bound to the free carrier before glucose binding, a characteristic concentration constant (Kc) was introduced to describe the relative importance of the sodium leak versus Na+-glucose cotransport currents. Kc represents the glucose concentration at which the Na+-glucose cotransport current is equal to the sodium leak. As both the sodium leak and the Na+-glucose cotransport current are predicted to occur after the binding of two sodium ions, the model predicted that Kc should be sodium-independent. However, by using a two-microelectrode voltage-clamp technique, the observed Kc was shown to depend strongly on the external sodium concentration ([Na+]o): it was four times higher at 5 mM [Na+]o than at 20 mM [Na+]o. In addition, the magnitude of the sodium leak varied as a function of [Na+]o in a Michaelian fashion, and the sodium affinity constant for the sodium leak was 2-4 times lower than that for cotransport in the presence of low external glucose concentrations (50 or 100 microM), whereas the current model predicted a sigmoidal sodium dependence of the sodium leak and identical sodium affinities for the sodium leak and the Na+-glucose cotransport. These observations indicate that the sodium leak occurs after one sodium ion is associated with the carrier and agree with predictions from a model with the binding order sodium-glucose-sodium. This conclusion was also supported by experiments performed where protons replaced Na+ as a "driving cation."

[Clinical and experimental study on rapid bladder ultrasound developer of Chinese medicinal herbs]

OBJECTIVE

To seek for a rapid type B ultrasound developer of Chinese medicinal herbs, so that the bladder and pelvic cavity developed clearly and pelvic cavity diseases could be diagnosed rapidly.

METHODS

One hundred and twenty-two patients were observed clinically and animal experiments were performed. The rapid bladder ultrasonography developer (RBUD-1, a preparation of Chinese herbal medicine) alone was used in Group 1, composite prescription of Western and Chinese medicine was used in group 2. The control groups were using lasix or mineral water.

RESULTS

Rapid diuresis and the decrease of the bladder capacity needed for development could be realized by Chinese medical herbs preparation, the difference between Group 1 and control group in developing time and bladder capacity were very significant. Results of animal experiments, which were referred to clinical grouping, showed the diuretic intensity of RBUD-1 within one hour was significantly higher than that in the other groups. Toxicological study showed the RBUD-1 was a non-toxic preparation.

CONCLUSION

RBUD-1 could effectively develop bladder and pelvic cavity, it would help to diagnose in time, on the other hand, it would also contribute for the combination imaging of Chinese and Western medicine.

Fast voltage clamp discloses a new component of presteady-state currents from the Na(+)-glucose cotransporter

The human Na(+)-glucose cotransporter (hSGLT1) has been shown to generate, in the absence of sugar, presteady-state currents in response to a change in potential, which could be fitted with single exponentials once the voltage had reached a new constant value. By the cut-open oocyte technique (voltage rising-speed approximately 1 mV/microsecond), phlorizin-sensitive transient currents could be detected with a higher time resolution during continuous intracellular perfusion. In the absence of sugar and internal Na+, and with 90 mM external Na+ concentration ([Na+]o), phlorizin-sensitive currents exhibited two relaxation time-constants: tau 1 increased from 2 to 10 ms when Vm decreased from +60 mV to -80 mV and remained at 10 ms for more negative Vm; tau 2 ranged from 0.4 to 0.8 ms in a weakly voltage-dependent manner. According to a previously proposed model, these two time constants could be accounted for by 1) Na+ crossing a fraction of the membrane electrical field to reach its binding site on the carrier and 2) conformational change of the free carrier. To test this hypothesis, the time constants were measured as [Na+]o was progressively reduced to 0 mM. At 30 and 10 mM external Na+, tau 1 reached the same plateau value of 10 ms but at more negative potentials (-120 and -160 mV, respectively). Contrary to the prediction of the model, two time constants continued to be detected in the bilateral absence of Na+ (at pH 8.0). Under these conditions, tau 1 continuously increased through the whole voltage range and did not reach the 10 ms level even when Vm had attained -200 mV while tau 2 remained in the range of 0.4-0.8 ms. These results indicate that 1) conformational change of the free carrier across the membrane must occur in more than one step and 2) Na+ binding/debinding is not responsible for either of the two observed exponential components of transient currents. By use of the simplest kinetic model accounting for the portion of the hSGLT1 transport cycle involving extracellular Na+ binding/debinding and the dual-step conformational change of the free carrier, tau 1 and tau 2 were fitted throughout the voltage range, and a few sets of parameters were found to reproduce the data satisfactorily. This study shows that 1) tau 1 and tau 2 correspond to two steps in the conformational change of the free carrier, 2) Na+ binding/debinding modulates the slow time constant (tau 1) and 3) a voltage-independent slow conformational change of the free carrier accounts for the observed plateau value of 10 ms.

rBAT is an amino acid exchanger with variable stoichiometry

The rBAT protein, when expressed in Xenopus oocytes, was previously shown to reproduce the selectivity of the Na(+)-independent neutral and basic amino acid transport system called bo,+. More recently, the capacity of rBAT to generate a transmembrane current was demonstrated when addition of neutral amino acids stimulated the efflux of cations (presumably basic amino acids) in rBAT-injected oocytes. In the present paper, aminoisobutyric acid (AIB), a neutral amino acid analogue, was shown to induce outward currents (efflux of basic amino acids) through rBAT similar to those caused by alanine in terms of affinity, maximal currents and I-V curves. Despite generating similar currents, the AIB transport rate was more than 30 times lower than that of alanine, thus challenging the assumption that rBAT functions as a classical exchanger. Experiments using a cut-open oocyte voltage clamp demonstrated that AIB was capable of stimulating rBAT-mediated currents from either side of the membrane. AIB, like alanine, was able to stimulate the efflux of radiolabeled alanine and arginine while no rBAT-mediated efflux was measurable in the absence of external rBAT substrates. These results demonstrate that (i) the presence of amino acids is required on both sides of the membrane for rBAT to mediate amino acid flux and thus rBAT must be some type of exchanger but (ii) rBAT-mediated amino acid influx is not stoichiometrically related to the efflux. A model of a "double gated pore" is proposed to account for these properties of rBAT, which contravene standard models of exchangers and other transporters.

Thermodynamic determination of the Na+: glucose coupling ratio for the human SGLT1 cotransporter

Phlorizin-sensitive currents mediated by a Na-glucose cotransporter were measured using intact or internally perfused Xenopus laevis oocytes expressing human SGLT1 cDNA. Using a two-microelectrode voltage clamp technique, measured reversal potentials (Vr) at high external alpha-methylglucose (alpha MG) concentrations were linearly related to In[alpha MG]o, and the observed slope of 26.1 +/- 0.8 mV/decade indicated a coupling ratio of 2.25 +/- 0.07 Na ions per alpha MG molecule. As [alpha MG]o decreased below 0.1 mM, Vr was no longer a linear function of In[alpha MG]o, in accordance with the suggested capacity of SGLT1 to carry Na in the absence of sugar (the "Na leak"). A generalized kinetic model for SGLT1 transport introduces a new parameter, Kc, which corresponds to the [alpha MG]o at which the Na leak is equal in magnitude to the coupled Na-alpha MG flux. Using this kinetic model, the curve of Vr as a function of In[alpha MG]o could be fitted over the entire range of [alpha MG]o if Kc is adjusted to 40 +/- 12 microM. Experiments using internally perfused oocytes revealed a number of previously unknown facets of SGLT1 transport. In the bilateral absence of alpha MG, the phlorizin-sensitive Na leak demonstrated a strong inward rectification. The affinity of alpha MG for its internal site was low; the Km was estimated to be between 25 and 50 mM, an order of magnitude higher than that found for the extracellular site. Furthermore, Vr determinations at varying alpha MG concentrations indicate a transport stoichiometry of 2 Na ions per alpha MG molecule: the slope of Vr versus In[alpha MG]o averaged 30.0 +/- 0.7 mV/decade (corresponding to a stoichiometry of 1.96 +/- 0.04 Na ions per alpha MG molecule) whenever [alpha MG]o was higher than 0.1 mM. These direct observations firmly establish that Na ions can utilize the SGLT1 protein to cross the membrane either alone or in a coupled manner with a stoichiometry of 2 Na ions per sugar, molecule.

[Quantitative analysis of synephrine in zhishi injection by RP-HPLC]

A reversed phase HPLC method was developed for the determination of synephrine in Zhishi Injection using methanol-water (1:1) containing sodium 1-pentane sulfonate (3.5%, G/V) and acetic acid (0.1%, V/V) as the mobile phase with UV detoction at 275nm. Linear response was obtained in the range of 8-64 micrograms/ml (r = 0.9998), the absolute recovery was 96.2-103.4%, and RSD 2.7%-6.0% (n = 7).

Growth hormone (GH) binding and effects of GH analogs in transgenic mice

Overexpression of human (h) or bovine (b) growth hormone (GH) in transgenic mice is associated with marked (2- to 12-fold) and significant increase in hepatic binding of GH and prolactin (PRL). This is due to an increase in the number of GH and PRL receptors (GHR, PRLR) per mg of microsomal protein without changes in binding affinity. Comparison of results obtained in transgenic animals expressing bGH with a mouse metallothionein (MT) or a rat phosphoenolpyruvate carboxykinase (PEPCK) promoter suggests that effects of bGH on hepatic GHR and PRLR do not require GH overexpression during fetal life and, within the dose range tested, the effects on PRLR are not dose dependent. The increase in hepatic GHR was accompanied by significant increases in plasma GH-binding protein (GHBP) and in mean residence time of injected GH. Thus, life-long elevation of peripheral GH levels alters the availability of both free GH and GHR. Site-directed in vitro mutagenesis was used to produce hGH and bGH analogs mutated within one of the sites involved in binding to GHR and PRLR. Mutating hGH to produce amino acid identity with bGH at Position 11, 18 (within Helix 1), 57, or 60 (within the loop between Helix 1 and 2) did not affect binding to GHR in vitro, or somatotropic activity in transgenic mice in vivo but reduced lactogenic activity in Nb2 cells by 22%-45%. Mutations of bGH designed to produce amino acid identity with hGH at one to four of the corresponding positions in the bGH molecule did not interfere with binding to GHR or somatotropic activity in vivo, and failed to produce significant binding to PRLR but resulted in alterations in the effects on the hypothalamic and anterior pituitary function in transgenic mice. Apparently region(s) outside the domains examined are essential for lactogenic activity of hGH, and different portions of the GH molecule are responsible for its diverse actions in vivo.

[A study on combined acupuncture and enflurane anesthesia for craniotomy]

The reinforcing effect of transcutaneous acupoint electric stimulation (TAES) with enflurane anesthesia during craniotomy was studied. 110 neurosurgical patients were randomly divided into three groups. Anesthesia was maintained with enflurane in group A (n = 40); in group B, enflurane anesthesia was supplemented by TAES with Han's acupoint nerve stimulator (HANS) at Hegu, Yuyao and Fengchi points on the operated side (n = 40); in group C, enflurane anesthesia was supplemented by TAES and scalp infiltration with 0.5% procaine (n = 30). The results showed that the minimum alveolar concentration (MAC) of enflurane in group B and C decreased 37.8-47.0% and 42.1-66.1% respectively than that in group A. The hemodynamics was more stable during operation, and the patients recovered faster after operation in group B and C. It was concluded that TAES with HANS significantly potentiated the anesthetic effect and decreased the side effects of enflurane during operation, and that the triple combination of TAES, enflurane and scalp infiltration with procaine proved to be a better anesthetic method for craniotomy.

Conversion of bovine growth hormone cysteine residues to serine affects secretion by cultured cells and growth rates in transgenic mice

GHs have been found to possess two disulfide bonds. We set out to determine the importance of bovine (b) GH's disulfide bonds relative to the ability of the hormone to be secreted by cultured cells in vitro and to promote growth in transgenic mice. We have generated six mutated bGH genes that encode serine (Ser) substitutions for cysteines (Cys). These mutated genes were used to generate bGH analogs in which either one or both disulfide bonds are destroyed. When the small loop of bGH was destroyed (Cys181-Ser or Cys189-Ser), the bGH analogs were found to be secreted by mouse L-cells at levels comparable to those of wild-type bGH. However, secretion was drastically reduced when the large loop was abolished (Cys53-Ser or Cys164-Ser). An immunofluorescence study of these bGH analogs revealed two distinct patterns of subcellular localization. Bovine GH analogs with mutations in the small loop demonstrated a perinuclear distribution similar to that of wild-type bGH, but analogs containing a disrupted large loop revealed a uniform cytoplasmic distribution pattern. When these mutated bGH genes were individually introduced into transgenic mice, only those animals that expressed bGH analogs with the large loop intact demonstrated a growth-enhanced phenotype. Transgenic mice that expressed bGH analogs lacking the large loop showed growth rates similar to those of nontransgenic mice. These results suggest that the integrity of the large loop, but not that of the small loop, is essential for the growth-enhancing activity of bGH in transgenic mice.

[Effects of superoxide dismutase on ischemic reperfusion injury in isolated working heart and cultured myocardial cells of rats]

An isolated working rat heart underwent 40 min of normothermic ceasing perfusion and 25 min of reperfusion. Superoxide dismutase (SOD) or/and mannitol were added to the perfusate 15 min before ceasing perfusion and 15 min after reperfusion. The results indicate that SOD (37,000 IU/L) improved significantly the contractile function of heart and increased the aortic output and coronary flow. Mannitol 0.02 mol/L provided additional benefit. The rat myocardial cells were cultured in the medium for 3 h with hypoxia followed by 2 h of reoxygenation. The content of lactic dehydrogenase (LDH) in the medium was increased and the degree of fluorescence polarization of myocardial cell membrane was raised. SOD was effective in preventing LDH release and decreasing the degree of fluorescence polarization. These results clearly demonstrate that ischemic reperfusion are capable of causing significant myocardial injury, which can be reduced or prevented by administration of oxygen free radical scavenger SOD.

Laboratory and clinical diagnosis of human cytomegalovirus infection after transplantation

Urine and blood specimens from 32 recipients of allograft organ transplant were investigated for human cytomegalovirus (HCMV) by conventional cell culture, indirect immunofluorescent assay subsequent to the rapid cell culture and DNA-DNA hybridization. The results showed that the rapid cell culture technique might be the best method for rapid detection of active HCMV infection after transplantation because it possesses the advantages of simplicity, speediness, sensitiveness, and high reliability of detecting productive HCMV infection. The major symptoms were prolonged or intermittent fever unresponsive to antibiotics, dysfunction or loss of function of the transplanted organ, pulmonary infiltrates and leukopenia. As our results suggested, reactivation of a latent infection appears to be the most probable etiologic factor contributing to HCMV infection after transplantation.

[Transpon Tn5 mutagenesis in Citrobacter]

When E. coli 1830/PJB4JI mating with four Citrobacter strains all were Kanamycin resistant, but a majority of KanrGens transconjugants were obtained from C-3-1. Among 3000 KanrGens 21 were auxotrophs, these are Lys-(1), Ura-(1), Arg-(2), Iso-(2), His-(2), Met-(1), Phe-(1), Tyr-(1), Ser-(1), Thr-(1), Leu-(3), Pro-(1), Ade-(3), Lac-(1), PJB4JI plasmid DNA were detected in parent strain E. coli 1830, but not in auxotrophs strains which carrying Tn5 induced mutations. Twenty auxotrophs chromosome DNA were hybridized with Tn5 DNA labeled with 32P respectively, all auxotrophs has positive reaction. Therefore, we concluded from genetic and physical data that auxotrophs resulted from Tn5 transposition from PJB4JI into C-3-1 chromosome.

[Effect of immobilization on the physical properties of cancellous bone: an experimental study]

40 adult new Zealand rabbits were divided into 6 groups, including a control group, which was free from immobilization. The left hind limb of each animal in the experimental groups was immobilized with the knee in extension by plaster cast for different period of time: 2,4,6,8 and 10 weeks for different group. The cancellous bone of upper tibia of each animal was tested systematically. The bone gravity, pointpressing strength, ash ratio and mineral content were measured and compared group by group to investigate their changes under different conditions. Following immobilization, the quantitative reduction of each parameter varied with the length of immobilization, marked in the first 6 weeks but gradually slowed down. It was most obvious in pointpressing strength, then mineral content, and the least the apparent gravity, denoting that the bone strength was most sensitive to immobilization. The reduction of mineral content exceeded that gravity, indicating the main loss was the former. Loss of point-pressing strength and mineral content was more prominent in the posterior part of the plateau, the weight-bearing area, than at the anterior and intercondylar parts. So was the metaphyseal area as compared with the epiphyseal area. In general, changes in bone gravity was directly in proportion with that of bone strength.

DNA probe technique for diagnosis of human cytomegalovirus infection

A rapid diagnostic assay for human cytomegalovirus (HCMV) has been developed for detecting HCMV DNA in urine samples with 32P-labelled cloned fragment, Eco RI fragment B, of DNA from HCMV strain Towne. 3.2 pg of homologous fragment from HCMV DNA could be detected by the labelled probe, and it did not hybridize DNA from other herpes viruses or human cells in dot hybridization assay. The assay correctly identified all (100%) of 7 coded urine specimen cultures positive for HCMV and 9 (90%) of 10 urine sample cultures negative for HCMV. So the hybridization assay was correct and as sensitive as the currently available tissue culture technique. The infection levels of different populations, such as organ transplantation recipients, patients with infantile hepatitis syndrome, normal infants, fetuses, have been investigated by the hybridization assay in the present study.

[A study on the pathogenesis of hepatolenticular degeneration using an in vitro model]

Hepatolenticular degeneration (HLD) as an autosomal recessively inherited disease has been known to be associated with by copper metabolic dysfunction. Its primary genetic defect is still not clear. The average copper content of HLD cells was found to be approximately threefold as much as that of normal cells in the authors previous studies. Cultured fibroblasts were used to serve as an in vitro model to investigate the primary molecular defects. The distribution of intracellular copper in the proteins of HLD cells were examined. The cell lysates were fractionated by gel chromatographic filtration. The copper concentration of the column fractions revealed that the copper binding character was altered in HLD cells. A decreased ratio of copper to proteins was observed in cytoplasmic proteins having a molecular weight greater than 300,000. There was more copper specifically bound to the lower molecular weight compounds in the HLD cells. The results of this laboratory technology suggested that this might serve as a method for establishing the early diagnosis of this disease.

Sensitivity of the recently infarcted heart to cardioplegic arrest. Beneficial effect of pretreatment with orotic acid

The mortality and morbidity of cardiac operations are increased in the presence of an established, recent myocardial infarct. To help understand the mechanisms for this and to develop a therapeutic strategy, we studied the response of the recently infarcted canine heart to hypothermic cardioplegia and the effect of pretreatment with orotic acid. Orotic acid is a precursor of nucleic acids with the ability to enhance protein synthesis. In 21 greyhound dogs, a myocardial infarct was produced by ligation of the left anterior descending coronary artery. Ten of these then received oral orotic acid (100 mg/kg/day) for 4 days and 11 were untreated. A sham group of eight dogs had a thoracotomy only and therefore had normal hearts (normal group). Four days later, all dogs underwent 60 minutes of cardioplegic arrest at 28 degrees C. Before arrest, stroke work index was lower and myocardial oxygen consumption at comparable work levels was higher in both the orotic acid and untreated infarct groups than in the normal group. After arrest and reperfusion, there was a severe depression of ventricular function in the untreated infarct group, with only 18% recovery of prearrest stroke work. In the orotic acid infarct group, recovery of prearrest function (43%) was similar to that in the normal group (56%) and significantly greater than in the untreated infarct group (p less than 0.01). After reperfusion, the untreated infarct group had a lower oxygen consumption, lower myocardial levels of adenosine triphosphate and glycogen, and higher lactate and water contents than before arrest (all p less than 0.05). In the orotic acid and normal groups, these variables returned to prearrest levels. We conclude that an established, recent myocardial infarct places the noninfarcted myocardium under stress and increases its sensitivity to hypothermic cardioplegia. This sensitivity is markedly reduced by treatment with orotic acid.

Comparison of the metabolic response of the hypertrophic and the normal heart to hypothermic cardioplegia. The effect of temperature

The aim of this study was to test for metabolic differences in the response of hypertrophic and normal hearts to hypothermic cardioplegia. Hypertrophic dog hearts and normal control hearts were subjected to 6 hours of hypothermic cardioplegia with the St. Thomas' Hospital solution. Levels before arrest of subepicardial and subendocardial adenosine triphosphate, creatine phosphate, and lactate in eight hypertrophic hearts were the same as those levels in 12 normal hearts. In hypertrophic hearts, but not in normal hearts, the induction of arrest was slow and was associated with an 11% increase in adenosine triphosphate levels, a 59% decrease in creatine phosphate levels, and a 12-fold increase in lactate levels. Seven hypertrophic hearts and eight normal hearts were studied during 6 hours of arrest and showed no further differences in metabolic response. Reducing the myocardial temperature from 20 degrees C to 12 degrees C slowed the rate of depletion of adenosine triphosphate and the rate of accumulation of lactate in both groups. We conclude that in the nonfailing, severely hypertrophic heart, levels before arrest of high-energy phosphates and lactate are normal, but that marked biochemical changes may occur if the induction of arrest is prolonged because of underdosing with cardioplegic solution. Cooling from 20 degrees C to 12 degrees C improves myocardial preservation in both hypertrophic and normal hearts.

A new technique of internal cardiac cooling improves atrial protection

We developed a technique for selectively cooling the right heart during cardioplegic arrest by intracavitary right atrial (RA) perfusion with cold blood. In dogs during hypothermic cardioplegic arrest, we compared the effects on myocardial temperature of RA perfusion and two snared caval cannulas with three methods of venous cannulation without perfusion: a two-stage atriocaval cannula, two caval cannulas and two snared caval cannulas. The mean atrioventricular (AV) node temperature with RA perfusion (16.5 degrees +/- 0.4 degrees C) was significantly lower than with the atriocaval cannula (25.1 degrees +/- 0.2 degrees C), two caval cannulas (25.2 degrees +/- 0.3 degrees C) or two snared caval cannulas (21.6 degrees +/- 0.2 degrees C) (p less than 0.01, RA perfusion versus other groups). The results for RA wall temperature showed a similar pattern. RA perfusion produced similar results in 6 patients undergoing coronary artery bypass grafting. We conclude that hypothermic protection of the right atrium and AV node is inadequate with conventional techniques of cannulation and cooling, and may be improved by the use of internal RA cooling.

Internal cardiac cooling improves atrial preservation: electrophysiological and biochemical assessment

This study was designed to determine if the improved hypothermia that can be achieved with cold perfusion of the right atrium is associated with improved atrial preservation. During 120 minutes of cardioplegic arrest, 7 dogs with occlusive caval cannulation underwent right atrial (RA) perfusion with cold blood and 7 dogs with a single atriocaval cannula served as controls. RA perfusion produced a lower atrial septal temperature than atriocaval cannulation, 96% less electrical activity during arrest, and a lesser prolongation of the A-H interval after reperfusion (40% versus 123%; p less than 0.01). At the end of arrest, compared with atriocaval cannulation, RA perfusion was associated with improved preservation of creatine phosphate (71 +/- 10% versus 40 +/- 7% of control; p less than 0.05) and a lower level of lactate in the RA wall (8 +/- 1 mumol/gm versus 15 +/- 2 mumol/gm; p less than 0.01). We conclude that improved hypothermia reduces electrical activity and anaerobic metabolism in the atrial myocardium during cardioplegic arrest and improves atrioventricular conduction following arrest.

Enhanced viral resistance in transgenic mice expressing the human beta 1 interferon

Recombinant plasmids pMTIF-beta 1A and pMTIF-beta 1B were constructed by fusing the metallothionein I promoter-regulatory region to the human beta 1 interferon (HuIFN-beta 1) gene. These linearized fusion genes were then introduced into mouse germ lines by zygote microinjection. The chromosomal integration and the germ line transmission of the injected DNA sequences in the resulting transgenic mice were detected by DNA dot blot and Southern transfer hybridizations. The sera of at least two strains of metallothionein/HuIFN transgenic mice were found to protect human WISH cells against vesicular stomatitis virus infection, and this activity could be neutralized by preincubation with anti-HuIFN-beta 1 antibody. These transgenic mice demonstrated significantly enhanced resistance to pseudorabies virus compared with nontransgenic mice when inoculated with pseudorabies virus. The level of resistance seemed to correlate with the concentrations of HuIFN-beta 1 in serum. These transgenic mice may be used as models to study IFN-induced responses and may serve as prototypes to generate disease-resistant animals.