Activation of intrinsic and synaptic currents in leech heart interneurons by realistic waveforms

Leech heart interneurons were voltage-clamped with realistic waveforms to investigate the currents underlying the oscillation in the cells. By estimating the leak current parameters in regions in which there was little contamination by voltage-gated currents, it was possible to measure the Ca2+ current, the persistent Na+ current, Ip, and the hyperpolarization-activated inward current, Ih. The experiments verified a prediction of a computer model of HN cells that the shape of the typical waveform was such that the low-threshold Ca2+ currents were partially inactivated during a slow up-ramp to a plateau potential. A step within the same range of the membrane potential as the realistic waveform produced > 4 times as much Ca2+ current. In two-cell voltage-clamp experiments, the step produced 20 times more graded inhibition than the normal presynaptic waveform. When the presynaptic heart interneuron oscillated with spikes, the graded inhibition was larger. The difference may arise from integration of a slowly decaying component of the spike-mediated inhibition. The persistent Na+ current had a very low threshold. During the most hyperpolarized phase of the waveform, Ip deactivated to 50% of its maximum conductance. A substantial part of Ip, therefore, was effectively contributing to the leak current in the HN cells. The h-current increased for waveforms that had longer periods, whereas increasing the h-current in the model reduced the period. The h-current thus provides negative feedback to perturbations that alter the period of the oscillation.     

Clinical profile of primary hyperparathyroidism in adolescents and young adults

The development of new strategies on chemotherapy of parasitic protozoan diseases is one of the most exciting research fields of recent years. World Health Organization (WHO) reports have recognized that the physiology and biochemistry of protozoan parasites and the host-parasite relation are the main targets for the design of new drugs that can be used in the future against these diseases.     

Changes in alveolar oxygen and carbon dioxide concentration and oxygen consumption during lung preservation. The maintenance of aerobic metabolism during lung preservation

Adult human liver microsomes supplemented with NADPH catalyzed the regioselective N-oxygenation of the aliphatic tertiary amine and S-oxidation of the phenothiazine sulfur atom of several 10-(N,N-dimethylaminoalkyl)phenothiazines. In addition, (+)- and (-)-4-bromophenyl-1,3-oxathiolane were converted to the corresponding S-oxides in the presence of NADPH and adult human liver microsomes. The (+) and (-) enantiomers of 4-bromophenyl-1,3-oxathiolane were converted to the S-oxides with low and high stereoselectivity, respectively. Studies on the biochemical mechanism for N-oxygenation of 10-(N,N-dimethylaminoalkyl)phenothiazines suggested that this reaction was catalyzed by the flavin-containing monooxygenase (form II), although cytochrome P-450 2D6 may also have contributed to N-oxide formation. S-Oxidation of chlorpromazine was catalyzed mainly by cytochrome P-450 3A. S-Oxidation of 10-(N,N-dimethylaminoalkyl)phenothiazines was catalyzed by a number of cytochromes P-450, including cytochromes P-450 2A6, 2C8, and 2D6. S-Oxygenation of (+)-4-bromophenyl-1,3-oxathiolane produced a mixture of the cis- and trans diastereomers in a process probably dependent on both hepatic monooxygenase systems. (-)-4-Bromophenyl-1,3-oxathiolane was converted almost exclusively to the trans-S-oxide in a process likely dependent on the adult human liver flavin-containing monooxygenase (form II). Development of regio- and stereochemical probes of adult human liver flavin-containing monooxygenase (form II) and cytochromes P-450 activity may be useful for eventual in vitro-in vivo correlations, but may require approaches quite distinct from that currently used for animal monooxygenases.     

Prion protein expression in Chinese hamster ovary cells using a glutamine synthetase selection and amplification system

BACKGROUND: Personnel working in neonatal intensive care units frequently face difficult ethical problems related to the initiation, maintenance or withdrawal of life support therapies. AIM: To assess the importance of ethical issues in the clinical decision making of health care providers in neonatal intensive care units. MATERIAL AND METHODS: A questionnaire based on five clinical vignettes that assessed judgments about quality of life, impact of parent's opinions and decision making in emergency situations and with different degrees of certainty, was designed. Eleven neonatologists and 20 nurses and midwives specialized in neonatology anonymously answered this questionnaire. RESULTS: There was a great inter individual variability in therapeutic approaches in cases with a bad vital and neurological prognosis. In cases of medical emergencies with uncertain diagnoses, bad vital prognosis but neurological indemnity, most professionals coincided in delivering all possible therapeutic options. Parent's opinions had a great impact in medical decisions, except when there was neurological indemnity. CONCLUSIONS: The specific responsibilities of the different agents in medical decision making must be delimited. Parents do not have absolute rights over their offspring and physicians must reject useless therapies.     

The relA/spoT-homologous gene in Streptomyces coelicolor encodes both ribosome-dependent (p)ppGpp-synthesizing and -degrading activities

Streptomyces coelicolor (p)ppGpp synthetase (Rel protein) belongs to the RelA and SpoT (RelA/SpoT) family, which is involved in (p)ppGpp metabolism and the stringent response. The potential functions of the rel gene have been examined. S. coelicolor Rel has been shown to be ribosome associated, and its activity in vitro is ribosome dependent. Analysis in vivo of the active recombinant protein in well-defined Escherichia coli relA and relA/spoT mutants provides evidence that S. coelicolor Rel, like native E. coli RelA, is functionally ribosome associated, resulting in ribosome-dependent (p)ppGpp accumulation upon amino acid deprivation. Expression of an S. coelicolor C-terminally deleted Rel, comprised of only the first 489 amino acids, catalyzes a ribosome-independent (p)ppGpp formation, in the same manner as the E. coli truncated RelA protein (1 to 455 amino acids). An E. coli relA spoT double deletion mutant transformed with S. coelicolor rel gene suppresses the phenotype associated with (p)ppGpp deficiency. However, in such a strain, a rel-mediated (p)ppGpp response apparently occurs after glucose depletion, but only in the absence of amino acids. Analysis of ppGpp decay in E. coli expressing the S. coelicolor rel gene suggests that it also encodes a (p)ppGpp-degrading activity. By deletion analysis, the catalytic domains of S. coelicolor Rel for (p)ppGpp synthesis and degradation have been located within its N terminus (amino acids 267 to 453 and 93 to 397, respectively). In addition, E. coli relA in an S. coelicolor rel deletion mutant restores actinorhodine production and shows a nearly normal morphological differentiation, as does the wild-type rel gene, which is in agreement with the proposed role of (p)ppGpp nucleotides in antibiotic biosynthesis.     

Cryptorchidism in boys with imperforate anus

In a retrospective study of the case reports of 136 boys who were operated on for an imperforate anus and who survived at least 18 months, cryptorchidism was the most common associated anomaly, involving 26 cases (19%). The higher the level of the anorectal malformations, the higher was the incidence of cryptorchidism. The incidence of renal and ureteric malformations and dysplasias showed a parallel tendency. The incidence of vertebral malformations and dysplasias in the T10-S5 area was low among patients with a covered anus or a perineal fistula. Cryptorchidism was found associated with urological and with T10-S5 vertebral malformations and dysplasias. Recognition of this association is probably new. The histopathological findings of testicular biopsy specimens and the location of the undescended testes in patients with an imperforate anus showed the same pattern as seen in undescended testes from patients with cryptorchidism only. These findings, together with the existing literature on the subject, indicate that further studies on the association of cryptorchidism, urological, and T10-S5 vertebral malformations and dysplasias may be very helpful toward a better understanding of cryptorchidism in general.