Cytokinetic and structural responses of the rat small intestine to riboflavin depletion

The impaired absorption and metabolism of Fe seen in riboflavin deficiency is attributed, at least in part, to a hyperproliferative response in the small intestine, associated with an altered morphology. Studies were conducted in female weanling Wistar rats to explore further the effect of riboflavin deficiency on the cytokinetics and structure of the small intestine. Feeding a riboflavin-deficient diet for 8 weeks from weaning resulted in a significantly lower villus number, a significant increase in villus length and an increased rate of transit of enterocytes along the villi, compared with weight-matched controls. A second experiment focused on the 3 weeks after weaning and showed that riboflavin deficiency inhibits the increase in villus number observed in control animals over this period. We suggest that riboflavin deficiency induced at weaning impairs the normal increase in villus number and that prolonged deficiency leads to an adaptive increase in length of villi and depth of crypts.

Acute lung injury following lung resection: is one lung anaesthesia to blame?

Further examination of the parameters of oxidative stress, perioperative changes in the vasoregulatory mechanisms of the pulmonary circulation, and characterisation of the endothelial insult that probably occurs in all patients undergoing lung resection is necessary if the operative conditions under which lung surgery is carried out are to be optimised. Perhaps, then, more insight might be gained into how to improve preservation of lungs for transplantation and how to protect the lung from significant injury following resection.

Lung injury in patients following thoracotomy

BACKGROUND

Postoperative lung injury is a recognised complication of thoracotomy for which there are few data regarding incidence and outcome.

METHODS

In a case controlled study the notes of all adult patients who developed acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) following thoracotomy between 1991 and 1994 were examined and classified according to the guidelines of the American Thoracic Society/European Respiratory Society for ALI/ARDS. The predictive value of a routine preoperative assessment and duration of anaesthesia in determining those patients most likely to develop ALI/ARDS was assessed.

RESULTS

Between 1991 and 1994 231 lobectomies, 103 pneumonectomies, and 135 wedge resections and segmentectomies were performed. The overall incidence of lung injury was 5.1%; 17 patients developed ARDS (two survived) and seven developed ALI (five survived). There was no significant difference compared with case matched controls in preoperative spirometric values, arterial oxygen tension (PaO2), or duration of anaesthesia. None of these parameters was useful in predicting those patients most likely to develop lung injury.

CONCLUSION

Lung injury after thoracotomy is associated with a high mortality. Conventional parameters for preoperative assessment do not predict those patients most likely to develop ALI/ARDS in these circumstances.

Neuroectodermal fate of epiblast cells in the distal region of the mouse egg cylinder: implication for body plan organization during early embryogenesis

The developmental fate of cells in the distal region (distal cap) of the epiblast was analysed by fate mapping studies. The displacement and differentiation of cells labelled in situ with carbocyanine dyes and lacZ-expressing cells grafted to the distal cap were studied over a 48-hour period of in vitro development. The distal cap epiblast differentiates predominantly into neurectodermal cells. Cells at the anterior site of the distal cap colonise the fore-, mid- and hindbrain and contribute to non-neural ectoderm cells of the amnion and craniofacial surface ectoderm. Those cells in the most distal region of the epiblast contribute to all three brain compartments as well as the spinal cord and the posterior neuropore. Cells at the posterior site of the distal cap are mainly localised to the caudal parts of the neural tube. A minor contribution to the embryonic (paraxial and lateral) and extraembryonic (allantoic and yolk sac) mesoderm is also found. Epiblast cells located outside the distal cap give rise to surface ectoderm and other non-ectodermal derivatives, with only a minor contribution to the neuroectoderm. Results of this study provide compelling evidence that the precursor population of the neural tube is contained in the distal cap epiblast of the early-primitive-streak-stage embryo. Furthermore, the regionalisation of cell fate within this small population suggest that a preliminary craniocaudal patterning may have occurred in the neural primordium before neurulation.

Morphological changes in the rat small intestine in response to riboflavin depletion

Female Wistar rats were weaned onto a diet deficient in riboflavin and compared with weight-matched and ad lib.-fed controls. The effects of riboflavin deficiency on villus morphometry and enterocyte number on the villi in the upper small intestine were studied. Riboflavin depletion was associated with increased villus length and a proportional increase in the number of cell positions along the villi. The total DNA, RNA and protein contents in the intestinal mucosa were not significantly different between any of the groups. Villus hypertrophy in the absence of increased cell number in the small intestine suggests that villus number may be reduced in riboflavin deficiency. Riboflavin deficiency did not influence the number of mucus-producing goblet cells or the amount of mucosal glycoprotein in the small intestine. Impaired production of mucus appeared not to be involved in the structural and functional changes seen in riboflavin deficiency.

Effects of olivocochlear bundle section on otoacoustic emissions in humans: efferent effects in comparison with control subjects

The effects of contralateral acoustic stimulation on evoked otoacoustic emissions (OAE) were examined in three subject groups in order that the impact of efferent olivocochlear bundle section (as a consequence of vestibular neurectomy) could be compared with normal findings, and with a control surgical population. Results demonstrated that the inhibitory effect of contralateral noise on OAE amplitude was absent from the cochlea with severed efferent fibers. These findings appear to be independent of acoustic reflex activity, as suppression was absent despite normal reflexes. Inter-aural suppression of emissions recorded from the patients' intact cochleae act as a control and show a clear reduction in amplitude during contralateral stimulation in a frequency specific pattern consistent with normal findings. Patients who had undergone a similar surgical approach for vascular decompression of the VIIIth nerve without vestibular nerve section, were studied in order to assess the impact of retrolabyrinthine surgery on inter-aural suppression. Inhibition of OAE amplitude was maintained in all control cases in both the operated and intact sides, and was consistent with suppression observed in normal subjects, suggesting that the surgical procedures had not disturbed inter-aural suppression of otoacoustic emissions. It is concluded that the olivocochlear efferent system, when activated by low level contralateral acoustic stimulation, has an inhibitory role in controlling the cellular mechanisms responsible for the generation of otoacoustic emissions in humans. OAE techniques in conjunction with contralateral acoustic stimulation may thus prove to be of value in providing a rapid and non-invasive clinical test of efferent function and offer a means of investigating the functional significance of the efferent auditory system in humans.

Expression of an X-linked HMG-lacZ transgene in mouse embryos: implication of chromosomal imprinting and lineage-specific X-chromosome activity

X-chromosome activity in female mouse embryos was studied at the cellular level using an X-linked lacZ transgene which encodes beta-galactosidase (beta-Gal). Translation of maternal RNA in oocytes is seen as beta-Gal activity that persists into early cleavage-stages. Zygotic transcription of the transgene from the maternal X chromosome (Xm) is first found at about the 8-cell stage. By contrast, expression of the lacZ transgene on the paternal X chromosome (Xp) is not seen until later at the 16-32-cell stage. Preferential inactivation of Xp occurs in the mural trophectoderm, the primitive endoderm, and derivatives of the polar trophectoderm, but a small number of cells in these lineages may still retain an active paternal X chromosome. X inactivation begins at 3.5 days in the inner cell mass but contrary to previous findings the process is not completed in the embryonic ectoderm by 5.5 to 6.0 days. Regional variation in beta-Gal activity is also observed in the embryonic ectoderm during gastrulation which may be related to the specification of cell fates. Random inactivation of Xp and Xm ensues in all somatic tissues but the process is completed at different times in different tissues. The slower progression of X inactivation in tissues such as the notochord, the heart, and the embryonic gut is primarily due to the persistent maintenance of two active X chromosomes in a significant fraction of cells in these tissues. Recent findings on the methylation of endogenous X-linked genes suggest that the prolonged expression of beta-Gal might also be due to the different rate of spreading of inactivation along the X chromosome to the lacZ transgene locus in different tissues.

Autosomal dominant polycystic kidney disease in Toronto

This study describes the Toronto, Ontario experience with autosomal dominant polycystic kidney disease (ADPKD). Patients were divided into three groups: Group 1, 19 families studied with genetic markers; Group 2, 80 pre-dialysis ADPKD patients followed by Toronto nephrologists in whom the incidence of non-renal complications and the mean age of onset of symptomatology is documented; Group 3, 4,449 individuals who entered end-stage renal failure (ESRF) in the Toronto region between the years 1981 and 1992, 320 with ADPKD and 4129 with other diseases. In this third group age of onset of ESRF, frequency, age and cause of death is compared between ADPKD and non-ADPKD. ADPKD caused by a gene different from that linked to chromosome 16 short-arm probes occurred at a frequency of between 8 and 17%. Incidence of hepatic cysts in ADPKD was similar to that of previous series, other organ involvement was underdiagnosed without deliberate screening, and incidence of symptomatic intracranial aneurysm was 1.25%. A 5% excess of patients with ADPKD died of cerebro-vascular accident. Years of survival after ESRF measured by life table analysis was significantly greater for ADPKD patients than for non-ADPKD patients. A high frequency of death due to infection still exists in ADPKD despite the reduction of invasive procedures in diagnosis and treatment, and despite the presumably improved recent methods of managing infection. The average age of onset of ESRF has been delayed by over six years, and average age of death of ADPKD patients at 63.9 years-old by 12.4 years since 1960.

Gastrulation in the mouse embryo: ultrastructural and molecular aspects of germ layer morphogenesis

Ultrastructural studies and lineage analyses of gastrulating mouse embryos have revealed that different morphogenetic tissue movements are involved in the formation of the three definitive germ layers. Definitive ectoderm is formed by epibolic expansion of the pre-existing progenitor population in the embryonic ectoderm. Formation of the mesoderm and the endoderm is initiated by cellular ingression at the primitive streak. The mesodermal layer is established by cell migration and cell sheet spreading, but the endoderm is formed by replacing the original primitive endodermal population. To this date, genes that are expressed during mouse gastrulation mostly encode cell surface adhesion or signalling molecules, growth factors and their receptors, and putative transcriptional factors. Their precise role during gastrulation remains to be investigated.

Algorithm to control "effect compartment" drug concentrations in pharmacokinetic model-driven drug delivery

In most computer-controlled pharmacokinetic model-driven drug infusion pumps, simulation of a linear compartmental pharmacokinetic model is used to compute the rate of intravenous drug infusion required to achieve setpoint central compartment (plasma) drug concentrations. For many drugs, it has been suggested that it is the drug concentration in a hypothetical "effect" compartment, rather than in the plasma, that should be manipulated to achieve maximum control over pharmacologic action. Controlling the effect compartment drug concentration is algorithmically more difficult than controlling the central compartment drug concentration because of the time delay between administration of drug into the central compartment and its subsequent appearance in the effect compartment. Presented in this paper is a model-based dosing algorithm for use in pharmacokinetic model-driven drug infusion devices that target the theoretical effect compartment drug concentration.

Recurrent primary liposarcoma of the pericardium: management by repeated resections

In 1979 we published a report of a patient with primary liposarcoma of the pericardium treated by surgical resection. Since then we have performed a total of seven resections on the same patient for recurrent liposarcoma, which have given excellent symptomatic relief, and her life was prolonged for 14 years. Repeated resection of recurrent liposarcoma of the mediastinum should always be considered as the appropriate management for these patients.

Buprenorphine and cocaine effects on social behavior of monkeys

We administered for 2 weeks intramuscular buprenorphine 0.3 mg/kg per day (and in a separate series, its vehicle) to each of 7 male, group-living Macaca fuscata (Japanese Snow Monkeys). Animals received one injection of cocaine 0.75 mg/kg and one of saline (about Days 9 and 14) in each series; after each of these doses ethologic observers recorded for 3 h the frequency of occurrence of 64 separate social, self-care, position and other behaviors. Cocaine alone changed the frequency of many behaviors. Buprenorphine alone only reduced the frequency of eating, yawning and ejaculation. The drugs had no interactive effects on behavior. In a dose reported to suppress monkeys' heroin and cocaine self-administration, buprenorphine showed remarkably few disruptions of normal group behavior. But it neither reversed nor enhanced cocaine's behavioral effects.

X-chromosome inactivation occurs at different times in different tissues of the post-implantation mouse embryo

During mammalian development, one of the two X chromosomes in female embryos is randomly inactivated in the somatic cell in order to achieve gene dosage compensation. But is X inactivation established simultaneously or is it accomplished over time in a lineage-dependent fashion? We have examined this question in mouse embryos carrying an X-linked lacZ transgene. This transgene is subject to inactivation and the loss of beta-galactosidase activity provides a direct indication of X inactivation in individual cells. We find that X inactivation proceeds with different schedules in different somatic tissues, and the notochord, the heart, cranial mesoderm and the hindgut are among the last tissues to undergo X inactivation.

Effects of contralateral acoustic stimulation on otoacoustic emissions following vestibular neurectomy

This study demonstrates that, following unilateral vestibular neurectomy, the inhibitory effect of contralateral acoustic stimulation on evoked otoacoustic emissions is absent. The patient acts as her own control in that the unoperated side shows normal suppression of otoacoustic emission amplitude with contralateral acoustic stimulation. The lack of interaural suppression of otoacoustic emissions on the sectioned side, in the presence of normal acoustic reflex threshold levels, provides evidence that observed phenomena are not merely a function of middle ear reflex activity. It is concluded that the lack of inhibition in the operated ear is due to the sectioning of the olivocochlear bundle within the inferior vestibular nerve, removing the efferent control of the receptor cells. Otoacoustic emissions recorded during contralateral acoustic stimulation may thus provide a rapid, non-invasive means of investigating the functional of the efferent auditory system.

Human dihydrofolate reductase: reduction of alternative substrates, pH effects, and inhibition by deazafolates

The kinetics of the NADPH-dependent reduction of 7,8-dihydrofolate, folate, and 7,8-dihydrobiopterin by human dihydrofolate reductase have been examined over the pH range from 4.0 to 9.5. The V and V/K profiles obtained with the three substrates indicate that a single ionizing residue at the active site of the enzyme must be protonated for catalysis. Both the maximum velocity of the reactions and the rate of interaction of the substrates with the enzyme-NADPH complex decrease in the order dihydrofolate greater than dihydrobiopterin much greater than folate. From the pK values of the V/K profiles, it can be concluded that, while dihydrofolate behaves as a sticky substrate and dihydrobiopterin exhibits slight stickiness, folate is not a sticky substrate. Further support for this conclusion comes from the results of deuterium isotope effects. The pK values obtained from both the V and V/Kfolate profiles are similar to the intrinsic pK value of 5.6 for both the free enzyme and the enzyme-NADPH complex. The folate analogue, 5-deazafolate, is not a substrate, but it undergoes strong interaction with the enzyme. This interaction, which is enhanced by the presence of NADPH, is due to protonation of the bound ligand that does not involve the single ionizing group at the active center of the enzyme. Difference spectra yield evidence for the protonation of bound 5-deazafolate and show that, on binding to the enzyme-NADPH complex, the pK of the N-8 atom is raised to about 10 from a value of about 4 in solution. The results are in accord with those of a recent paper on the three-dimensional structure of the enzyme-5-deazafolate complex [Davies, J.F., Delcamp, T.J., Prendergast, N.J., Ashfors, V.A., Freisheim, J.H., & Kraut, J. (1990) Biochemistry 29, 9467-9479] which indicate that there is hydrogen bond formation between N-8 of the ligand and the carbonyl group of Ile-7. However, the present findings do not support the idea that bound 5-deazafolate resembles the transition-state complex for folate reduction. Quinazolines also interact strongly with the enzyme but in a pH-independent manner. The dissociation constants for the binary complexes are an order of magnitude lower than that for the binding to the enzyme of unprotonated 5-deazafolate. This difference reflects the hydrophobic nature of the amino acid residues at the active site that are near the N-5 and N-8 nitrogens of bound pterins.

Cocaine, social behavior, and alcohol-solution drinking in monkeys

Eight group-living male monkeys received cocaine (0 to 3.0 mg/kg) individually or as a group. Cocaine suppressed social affiliative behaviors, eating, and drinking (of both alcohol and control solutions). It induced bizarre stereotypies, hypervigilance, panic-like fleeing, enhancement and then suppression of locomotion, and a seizure. Cocaine had little effect on aggressiveness or sexual behavior. Proportion of time spent lying or sitting changed significantly. Cocaine produced severe behavioral abnormality in this social setting.

Medical and social outcome in adolescents with end-stage renal failure

Clinical information was collected on 118 adolescents who developed ESRF at age 143 months or older and were treated between 1966 and 1986 at the Toronto Hospital for Sick Children. The cumulative survival rate in transplanted patients (N = 109) was 80.1% after 15 years. Survival rates after four years were 93.9% in transplanted and 46.9% in nontransplanted patients (P less than 0.001). No patient receiving dialysis alone (N = 9) was followed longer than four years. Nine patients received three transplants and had an 89% survival rate. Six of these had a functioning graft at end of the follow-up. The cumulative survival of the entire group was 76.4% at eighteen years. Forty-two (35.6%) patients had a height below the third percentile. Functional status obtained by a structure telephone interview with a member of the present treating nephrology service was good (G) or excellent (E) for 66.7% of all patients (73.5% of transplant patients (N = 68) and 45% of dialysis patients (N = 20). Hemodialysis patients functioned less well [25% G/E (N = 12)] than peritoneal dialysis patients [75% G/E (N = 8)]. Most patients achieved an appropriate level of formal education although more slowly than normal adolescents. Only 11 patients were neither enrolled in an educational institution nor employed. We conclude that aggressive treatment for adolescents with ESRF is an appropriate application of health care resources.

Characterization of strains of Helicobacter pylori: one-dimensional SDS-PAGE as a molecular epidemiologic tool

One-dimensional linear sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total proteins, coupled with a computerized numerical analysis, was used to distinguish among strains of Helicobacter pylori. One hundred seventy-five clinical strains and five reference strains of H. pylori from humans, four isolates of Helicobacter mustelae from ferrets, and three isolates of H. pylori-like organisms (HPLOs) from miniature swine were examined. Intraspecies and interspecies comparisons were made through a numerical analysis of protein profiles. It was possible to make valid comparisons for strains run on a single gel. However, variations between gels were significant in some cases, and strains from these gels were not compared. Multiple isolates of H. pylori from one patient clustered at greater than 90% similarity. All strains of H. pylori clustered at greater than 60% similarity, whereas H. pylori was clearly distinguishable (less than 40% similarity) from both H. mustelae and HPLOs. An eventual application of this technique will be to determine whether relapse following therapeutic intervention is due to reinfection (from an exogenous source) or to recrudescence.