Direct channel-gating and modulatory effects of triiodothyronine on recombinant GABA(A) receptors

We have previously shown that triiodothyronine (T3) inhibits gamma-aminobutyric acid type A (GABA(A)) receptors in synaptoneurosomes and transfected cells. To further characterize this phenomenon, the effect of T3 on recombinant GABA(A) receptors expressed in Xenopus oocytes was investigated using the two-electrode voltage-clamp method. T3 inhibited GABA-gated chloride currents in a non-competitive manner and yielded an IC50 of 7.3 +/- 0.8 microM in oocytes coexpressing alpha1beta2gamma2L receptor subunits. T3 had no inhibitory effect on alpha6beta2gamma2L or beta2gamma2L receptor constructs, indicating that the alpha1 subunit imparts T3 sensitivity to the receptor. In addition to the inhibitory effect of T3 on GABA responses, T3 alone induced a current in oocytes expressing alpha1beta2gamma2L, alpha6beta2gamma2L and beta2gamma2L constructs. This current displayed a reversal potential identical to that of GABA-gated chloride currents, and was blocked by picrotoxin (10 microM), but not by bicuculline (50 microM), indicating that T3 gates the chloride channel by binding to a site other than the GABA-binding site. The direct channel-gating action of T3 was concentration-dependent, with an EC50 of 23 +/- 5 microM. The actions of T3 are unique in that T3 acts as a noncompetitive antagonist in the presence of GABA but can directly gate the chloride channel in the absence of GABA.

Physical assault in New Zealand: the experience of 21 year old men and women in a community sample

AIM

To obtain epidemiological information on physical assault in a high risk group of New Zealanders.

METHOD

Rates of physical assault in the preceding twelve months were ascertained by interview in a cohort of 21 year old, Dunedin-born men (n = 482) and women (n = 462).

RESULTS

Forty-five percent of the men and one quarter of the women reported at least one physical assault, either completed, attempted or threatened. A small proportion of these received medical treatment. Most serious assaults were by a perpetrator who was thought to have been drinking alcohol. Most assaults on men were by strangers but partners carried out more assaults against women, especially those receiving medical treatment. One quarter of all assaults on women were by other women, compared to 15% of the assaults on men. Differences between patterns of assaults on women and on men are discussed.

CONCLUSION

It is important for doctors to be aware of the widespread occurrence of interpersonal violence in New Zealand and its underreporting.

Does withholding gonadotrophin administration prevent severe ovarian hyperstimulation syndrome?

Withholding gonadotrophin administration (coasting) may prevent severe ovarian hyperstimulation syndrome (OHSS). To ascertain the effectiveness of this protection a cohort of 252 consecutive in-vitro fertilization (IVF) or IVF with intracytoplasmic sperm injection (ICSI) cycles was studied. Twenty women with exaggerated response were treated with coasting. Despite coasting, four patients developed severe OHSS requiring hospitalization. Two of these four patients also required paracentesis. Multiple regression analysis in coasting cycles revealed severe OHSS was related to youth, number of oocytes retrieved and serum oestradiol prior to human chorionic gonadotrophin (HCG). Risk of developing severe OHSS was multifactorial and not necessarily prevented by withholding gonadotrophin.

Histologic findings of transmyocardial laser channels after two hours

Histologic examination of the human myocardium has been performed several days, weeks, and months after transmyocardial laser revascularization. We performed microscopic examinations 2 hours postoperatively. In addition to the patent channel (diameter, 1 mm) and a 1-to 2-mm rim of necrosis, a 1- to 3-mm zone of myofibrillary degeneration was found. This additional reversible injury immediately after transmyocardial laser revascularization could explain the higher mortality rate in patients with reduced left ventricular function.

Morphology of basal optic tract terminals in the turtle, Pseudemys scripta elegans

The morphologies of axon terminals of retinal ganglion cells projecting to the basal optic nucleus (BON) via the basal optic tract (BOT) were studied in the red-eared turtle. The BOT was visualized on the ventral surface of the brainstem in vitro, and either biotinylated dextran amine was injected extracellularly or neurobiotin was injected into physiologically identified axons during intracellular recordings. Up to 16 hours after tracer injection, the brains were fixed, sectioned parasagittally, and stained for biotin and Nissl substance. The diameters and depths of extracellularly filled axons were measured at three BON sites. Fourteen axons were reconstructed from serial sections with the aid of appropriate computer software. Analysis of extracellularly filled retinal axons revealed that about three times more axons were present just inside the rostral border of the BON compared with its caudal border. Thick (2-4 microm) axons were located within 100 microm from the ventral border, whereas thin (<2 microm) axons were found throughout the nucleus. Only the thinnest axons (<1 microm) extended caudally from the nucleus, indicating that some extracellularly labelled fibers passed through the BON. The intracellularly filled axons were more similar to the thick axons filled extracellularly and arborized entirely within the BON. All of the intracellularly filled axons had thick ventral trunks from which many thin branches extended dorsally and obliquely within the BON. The thin branches bifurcated repeatedly to form bead-like varicosities or boutons that often formed clusters within regions of 150 microm3 or less. These clusters may reflect areas of focused synaptic contact on BON cells with specific direction preferences.

The use of alternative therapies by children with asthma: a brief report

OBJECTIVE

To identify the nature and prevalence of alternative therapies used by children with asthma attending a children's hospital.

METHODOLOGY

Subjects consisted of a consecutive series of 51 children with asthma aged 1-6 years who were attending the Women's and Children's Hospital, South Australia. Parents of the children completed a questionnaire describing the use of alternative therapies by the children.

RESULTS

Approximately 55% of children used alternative therapies for asthma management. Therapies used most commonly were massage, relaxation exercises, diet therapy and vitamins. There was no significant difference in the age, asthma severity, length of time since diagnosis or presence of another illness amongst children who did or did not use alternative therapies.

CONCLUSIONS

A substantial proportion of children with asthma who attend paediatric clinics use alternative therapies. Paediatricians should be aware of this and be prepared to discuss alternative therapies with parents. This may facilitate more open doctor-patient relationships and better management of children's asthma.

Protein folding assisted by the GroEL/GroES chaperonin system

The chaperonin system GroEL/GroES assists in the folding of proteins in the bacterial cytosol. Recent applications of biophysical techniques for the structural analysis of GroEL, GroES, and chaperonin-bound protein folding intermediates have provided the basis for understanding the molecular mechanism of GroEL/GroES action. GroEL, a double-ring complex, binds unfolded proteins at its inner ring surface. Protein folding proceeds in the central cavity of GroEL, after dissociation of the polypeptide has been triggered by ATP hydrolysis in GroEL. Premature release of unfolded protein into external solution is prevented by binding of the cofactor GroES on top of the GroEL cylinder, resulting in an enclosed cage. Upon ATP-dependent dissociation of GroES, substrate protein is eventually released from GroEL in a native or native-like conformation. While current in vitro results about the structure, function, and molecular mechanism of GroEL/GroES-assisted protein folding have led to a quite detailed picture of this complex process, the extent to which the GroEL/GroES system actually participates in the folding of newly-synthesized proteins in the cell is less defined and remains a subject for further studies. Ingenious biochemical and genetic approaches will be necessary to show whether our current view of chaperonin action indeed accurately reflects its modus operandi inside a living cell.

Role of the GroEL chaperonin intermediate domain in coupling ATP hydrolysis to polypeptide release

Modification of the Escherichia coli chaperonin GroEL with N-ethylmaleimide at residue Cys138 affects the structural and functional integrity of the complex. Nucleotide affinity and ATPase activity of the modified chaperonin are increased, whereas cooperativity of ATP hydrolysis and affinity for GroES are reduced. As a consequence, release and folding of substrate proteins are strongly impaired and uncoupled from ATP hydrolysis in a temperature-dependent manner. Folding of dihydrofolate reductase at 25 degrees C becomes dependent on GroES, whereas folding of typically GroES-dependent proteins is blocked completely. At 37 degrees C, GroES binding is restored to normal levels, and the modified GroEL regains its chaperone activity to some extent. These results assign a central role to the intermediate GroEL domain for transmitting conformational changes between apical and central domains, and for coupling ATP hydrolysis to productive protein release.

Use of low-dose OKT3 as induction therapy in liver transplantation

BACKGROUND

A pilot study was performed to prospectively evaluate the safety and efficacy of "low-dose" OKT3 induction after liver transplantation.

METHODS

Sixteen patients received a 5- to 10-day course of OKT3 (2.5 mg i.v. daily) along with azathioprine, prednisone, and the delayed introduction of cyclosporine (Neoral).

RESULTS

Patient and graft survival rates at 1 year were 88% and 82%. Five patients (31%) had biopsy-proven rejection; all five were treated successfully with steroids. There were 15 infections in 12 patients, including 5 cytomegalovirus infections. Adverse events attributed to OKT3 consisted of low-grade fever (five patients), transient hypoxemia (three patients), and transient hypotension (two patients). Pharmacy acquisition costs for OKT3 averaged $2,139 less as compared to a group of historical controls receiving full-dose therapy.

CONCLUSIONS

Low-dose OKT3 induction appears to be a safe and useful method of postoperative immunosuppression after liver transplantation. Its ultimate clinical, immunologic, and economic efficacy awaits determination by randomized trial.

Inhibition of virus-encoded thymidine kinase suppresses herpes simplex virus replication in vitro and in vivo

Both herpes simplex virus type 1 (HSV-1) and HSV-2 encode a thymidine kinase enzyme which differs from cellular thymidine kinase in substrate specificity. Viral thymidine kinase enables the virus to replicate in cells that lack cellular thymidine kinase, namely those of the sensory neurons where the virus establishes, and periodically reactivates from, a latent state. Thymidine kinase-dependent HSV replication following viral reactivation at the site of latency is thought to precede the emergence of virus at mucosal surfaces. The ability to inhibit such an essential viral enzyme would potentially prevent HSV from replicating within neuronal tissue, and thus stop the recurrent disease cycle. Ro 32-2313 was designed as a selective and competitive inhibitor of HSV thymidine kinase and in vitro studies have confirmed this mechanism of action. In vivo evaluation of a soluble prodrug of Ro 32-2313, Ro 32-4397, was undertaken in murine models where pathogenesis was dependent upon viral replication in neuronal tissue. It was shown that in vivo administration of Ro 32-4397 (i) significantly reduced the viral titre detected in isolated dorsal root ganglia; (ii) prevented HSV-2-induced lethality in a systemic infection model; and (iii) reduced zosteriform lesion development in a model of dermal infection. Administration of Ro 32-4397 produced dose-related changes in viral pathogenicity towards those of the phenotype of a thymidine kinase-deficient virus. Overall, the study confirmed that thymidine kinase inhibitors can suppress the replication of HSV in vivo, and suggest that such inhibitors may reduce reactivation of the virus from latency if used prophylactically in recurrent HSV infection.

Transmyocardial laser revascularization (TMLR) in patients with unstable angina and low ejection fraction

OBJECTIVE

Does perioperative use of the intraaortic balloon pump (IABP) improve the postsurgical outcome of patients presenting with endstage coronary artery disease, unstable angina and low ejection fraction transferred for transmyocardial laser revascularization (TMLR)?

METHODS

TMLR, as sole therapy combined with the perioperative use of an intraaortic balloon pump has been assessed in seven patients with endstage coronary artery disease, unstable angina and low ejection fraction (EF < 35%). Six out of seven patients had signs of congestive heart failure. These patients are compared with 23 patients with endstage coronary artery disease, stable angina and EF > 35%, who were treated with TMLR as sole therapy without the use of IABP. The creation of transmural channels was performed by a CO2-laser. All patients were evaluated by hybrid positron emission tomography (perfusion SPECT and viability PET) and ventriculography preoperatively. Echocardiography, clinical status and hemodynamic assessment by Swan Ganz catheter were performed perioperatively.

RESULTS

The perioperative mortality of this combined procedure (TMLR and IABP) was zero. Three out of seven patients had pneumonia with complete recovery. Swan Ganz catheter examinations showed deterioration of LV-function after TMLR intraoperatively and improvement after 2 h and further after 6 h on ICU (P < 0.05). In contrast, a decrease of LV-function in sole TMLR patients with an EF > 35%) has not been observed. Patients with EF < 35% needed the IABP for 2.3 days and moderate dose catecholamines for a mean of 3.0 days. The postoperative EF and resting wall motion score index (WMSI) of all analysed LV segments (evaluated by echocardiography) did not change compared to baseline (EF 31.3+/-2.6 preop. to 32.8+/-3.2 postop.; WMSI: 1.75+/-0.14 at baseline to 1.71+/-0.17 postop.). The average Canadian Angina Class at the time of discharge decreased from 4.0+/-0 (baseline) to 2.3+/-0.5 (P < 0.05) and the NYHA-Index from 3.9+/-0.3 to 2.7+/-0.5. No patient had signs of angina pectoris, whereas two patients still had signs of congestive heart failure.

CONCLUSIONS

The reported data support our concept to start IABP preoperatively in patients with reduced LV contractile reserve in order to provide cardiac support during the postoperative phase of reversible decline of LV-function induced by TMLR.

The stigma of severe mental illness: some potential solutions for a recalcitrant problem

Despite recent advances in the treatment of individuals with severe mental illness (SMI), their full integration into society is hindered by lingering negative attitudes towards them. In this paper, a brief overview is provided on stigmatization towards individuals with SMI, including its' impact on quality of life and self-esteem, as well as the factors which likely underlie it. Research is reviewed showing that lowered negative perceptions towards persons with SMI are associated with previous contact with this population and with presentation of empirically-based information on the association between violence and SMI. Limitations of these findings are discussed with an eye towards developing improved techniques for reducing stigma.

A variable intron distribution in globin genes of Chironomus: evidence for recent intron gain

The intron positions found in globin genes of plants, protozoa and invertebrates have been interpreted as evidence for a three-intron-four-exon structure of the ancestral globin gene. In particular, the so-called 'central' introns, which are not found in vertebrate globin genes but are present in a variety of invertebrate and plant species, have been used as an argument for an ancestral gene structure featuring three introns. We have analyzed the presence or absence of central introns in the Gb genes 2beta, 9 and 7A of various European and Australasian species of the insect Chironomus. We find unrelated central introns at different positions in some of the species investigated, while other species completely lack introns in these genes. This variable distribution of introns is parsimoniously explained by independent intron additions. Such a gain of introns may occur convergently at identical positions in unrelated taxa. Insertion by gene conversion may be a viable mechanism to explain intron gain.

Vascular endothelial growth factor stimulates prostacyclin production and activation of cytosolic phospholipase A2 in endothelial cells via p42/p44 mitogen-activated protein kinase

Vascular endothelial growth factor (VEGF) stimulated a time- and concentration-dependent increase in PGI2 synthesis in human umbilical vein endothelial cells with a mean maximum increase of 2-fold above basal levels at 25 ng/ml after 60 min. VEGF also rapidly stimulated the release of arachidonic acid and phosphorylation and activation of cytosolic phospholipase A2 (cPLA2). The VEGF-related factor, placenta growth factor (PIGF), had little effect on PGI2 synthesis, arachidonic acid release or cPLA2 activation. PD98059, a selective inhibitor of MAP kinase kinase, caused complete inhibition of VEGF-stimulated MAP kinase activity, PGI2 synthesis and cPLA2 gel retardation, but had no effect on VEGF-induced vWF secretion. These findings provide the first evidence that VEGF can stimulate PGI2 synthesis via cPLA2-mediated arachidonic acid release and indicate that VEGF stimulation of this biosynthetic pathway may occur, at least in part, via activation of p42/p44 MAP kinases.

A cell surface tethered enzyme improves efficiency in gene-directed enzyme prodrug therapy

The potential for expressing the bacterial enzyme carboxypeptidase G2 (CPG2) tethered to the outer surface of mammalian cells was examined for use in gene-directed enzyme prodrug therapy. The affinity of CPG2 for the substrate methotrexate was unaffected by three mutations required to prevent N-linked glycosylation. Breast carcinoma MDA MB 361 cells expressing CPG2 internally showed only a very modest increase in sensitivity to the prodrug CMDA because the prodrug did not enter the cells. Cells expressing surface-tethered CPG2, however, became 16-24-fold more sensitive to CMDA and could mount a good bystander effect. Systemic administration of CMDA to mice bearing established xenografts of the transfected cells led to sustained tumor regressions or cures.

Postexercise protein-carbohydrate and carbohydrate supplements increase muscle glycogen in men and women

We have previously demonstrated that women did not increase intramuscular glycogen in response to an increased percent of dietary carbohydrate (CHO) (from 60 to 75% of energy intake) (M. A. Tarnopolsky, S. A. Atkinson, S. M. Phillips, and J. D. MacDougall. J. Appl. Physiol. 78: 1360-1368, 1995). CHO and CHO-protein (Pro) supplementation postexercise can potentiate glycogen resynthesis compared with placebo (K. M. Zawadzki, B. B. Yaspelkis, and J. L. Ivy. J. Appl. Physiol. 72: 1854-1859, 1992). We studied the effect of isoenergetic CHO and CHO-Pro-Fat supplements on muscle glycogen resynthesis in the first 4 h after endurance exercise (90 min at 65% peak O2 consumption) in trained endurance athletes (men, n = 8; women, tested in midfollicular phase, n = 8). Each subject completed three sequential trials separated by 3 wk; a supplement was provided immediately and 1-h postexercise: 1) CHO (0.75 g/kg) + Pro (0.1 g/kg) + Fat (0.02 g/kg), 2) CHO (1 g/kg), and 3) placebo (Pl; artificial sweetener). Subjects were given prepackaged, isoenergetic, isonitrogenous diets, individualized to their habitual diet, for the day before and during the exercise trial. During exercise, women oxidized more lipid than did men (P < 0.05). Both of the supplement trials resulted in greater postexercise glucose and insulin compared with Pl (P < 0.01), with no gender differences. Similarly, both of these trials resulted in increased glycogen resynthesis (37.2 vs. 24. 6 mmol . kg dry muscle-1 . h-1, CHO vs. CHO-Pro-Fat, respectively) compared with Pl (7.5 mmol . kg dry muscle-1 . h-1; P < 0.001) with no gender differences. We conclude that postexercise CHO and CHO-Pro-Fat nutritional supplements can increase glycogen resynthesis to a greater extent than Pl for both men and women.