Medical equipment costs: those you see and those you pay

On day 21.5 a pregnant rat received a single injection of [1-14C]glycerol. The purpose was to study the transfer of glycerol through the placenta from the maternal to fetal plasma. From 3-20 min after injection the specific activity of glycerol in maternal and fetal plasma was measured. The results indicate that the mother can provide this molecule to the fetus. Similar results were obtained with the rabbit on day 28 of pregnancy. The possibility of the conversion of plasma glycerol to glucose has been investigated in the rat and rabbit fetus. This molecule was chosen chiefly to see whether the gluconeogenic pathway was functioning in the fetus above the triose phosphate step. At two stages of fetal development the capacity of the fetus to incorporate [1-14C]glycerol into glucose plus glycogen has been shown in the two species. In the rat fetus the conversion of [1-14C]glycerol to [14C]glucose increases from 19.5 to 21.5 days of gestation. For the rabbit this parameter increases from 25 to 28 days of gestation. On day 25 in the rabbit and day 19.5 in the rat the liver glycogen was labeled, but it did not accumulate the [14C]glucose from [1-14C]glycerol during the time that we have studied. In contrast, on day 28 in the rabbit and day 21.5 in the rat the incorporation of radioactivity increased as function of the time. However, the relative importance of glycerol as precursor of the glucose plus glycogen in the fetus remains to be elucidated.     

The effects of pentobarbitone and chloralose anaesthesia on the vagal component of bronchoconstriction produced by histamine aerosol in the anaesthetized dog

1 Total lung resistance (R(L)) and dynamic lung compliance (C(dyn)) were measured in dogs anaesthetized with pentobarbitone or chloralose and subjected to aerosols of histamine during 4 successive inspirations.2 Histamine caused concentration-dependent increases in R(L) and decreases in C(dyn). A significant vagal component was involved, but only when chloralose was employed and then only in the R(L) response.3 The resting values of R(L) and C(dyn) were similar regardless of which anaesthetic was used and remained essentially the same if the vagi were cooled.4 Electrical stimulation of the efferent vagi caused large increases in R(L) of dogs given chloralose and these effects were attenuated by the administration of pentobarbitone. Such stimulation was relatively ineffective in dogs given pentobarbitone alone.5In vitro, electrical field stimulation caused contractions of dog trachealis muscle. The responses were reduced by pentobarbitone in concentrations approximating to plasma levels in the anaesthetized dogs (1 to 5 x 10(-4) M), but the effects of exogenous acetylcholine were unaltered. The inhibition was dose-dependent, reversed by washing and unaltered by hexamethonium.6 The results suggest that pentobarbitone inhibits the vagal component of histamine-induced bronchoconstriction in the dog by an action on the efferent pathway. Furthermore, pentobarbitone acts either by blocking transmission along postganglionic parasympathetic nerves or by preventing the release of acetylcholine from the nerve endings in the lung.     

Metabolism of glucose, fructose and lactate in vivo in chronically cannulated foetuses and in suckling lambs

1. Chronically cannulated sheep foetuses and suckling lambs were injected with 14C-labelled glucose, fructose or lactate, and sequential blood samples taken under conditions of minimal stress and without anaesthesia. 2. Gluconeogenesis from lactate was not detectable in foetal sheep, but the pathway was active in suckling lambs. 3. Fructose utilization rates were low in foetal sheep, with no measurable conversion into glucose or lactate. 4. The high rates of irreversible loss of both glucose and lactate in the foetus were decreased in suckling lambs. Radioactivity from labelled glucose entered both the lactate and fructose pools in foetal sheep, and entered the lactate pool in suckling lambs. 5. A model is proposed in which carbon flow between glucose, fructose and lactate has been quantified in foetal sheep.     

Germ-line mutations in the neurofibromatosis 2 gene: correlations with disease severity and retinal abnormalities

Neurofibromatosis 2 (NF2) features bilateral vestibular schwannomas, other benign neural tumors, and cataracts. Patients in some families develop many tumors at an early age and have rapid clinical progression, whereas in other families, patients may not have symptoms until much later and vestibular schwannomas may be the only tumors. The NF2 gene has been cloned from chromosome 22q; most identified germ-line mutations result in a truncated protein and severe NF2. To look for additional mutations and clinical correlations, we used SSCP analysis to screen DNA from 32 unrelated patients. We identified 20 different mutations in 21 patients (66%): 10 nonsense mutations, 2 frameshifts, 7 splice-site mutations, and 1 large in-frame deletion. Clinical information on 47 patients from the 21 families included ages at onset and at diagnosis, numbers of meningiomas, spinal and skin tumors, and presence of cataracts and retinal abnormalities. We compared clinical findings in patients with nonsense or frameshift mutations to those with splice-site mutations. When each patient was considered as an independent random event, the two groups differed (P < or = .05) for nearly every variable. Patients with nonsense or frameshift mutations were younger at onset and at diagnosis and had a higher frequency and mean number of tumors, supporting the correlation between nonsense and frameshift mutations and severe NF2. When each family was considered as an independent random event, statistically significant differences between the two groups were observed only for mean ages at onset and at diagnosis. A larger data set is needed to resolve these discrepancies. We observed retinal hamartomas and/or epiretinal membranes in nine patients from five families with four different nonsense mutations. This finding, which may represent a new genotype-phenotype correlation, merits further study.     

Use of cardiopulmonary bypass to salvage patients with multiple-chamber heart wounds

BACKGROUND: The need for cardiopulmonary bypass in the treatment of penetrating heart injuries is debated. OBJECTIVES: To review our experience with penetrating heart injuries and determine the indications and outcome for cardiopulmonary bypass. DESIGN: Retrospective review. SETTING: A university-based, level I trauma center. PATIENTS: All victims of penetrating heart injury presenting between July 1, 1989, and December 31, 1995. METHODS: Medical records were reviewed for demographic and physiological data, operative findings, and outcome. RESULTS: Overall survival for 106 patients with penetrating heart injury was 55%. In an effort to resuscitate the heart, 4 patients with unresponsive cardiogenic shock were placed on cardiopulmonary bypass; none survived. Of 30 patients with multiple-chamber injuries, 11 presented with signs of life and 7 survived. Cardiopulmonary bypass was essential to repair complex injuries in 2 of the 7 survivors. CONCLUSION: Cardiopulmonary bypass was ineffective in salvaging patients with cardiogenic shock but was essential in some patients with complex multiple-chamber cardiac injuries that could not be exposed and repaired by other means.     

The Australian brushtail possum (Trichosurus vulpecula) gonadotrophin alpha-subunit: analysis of cDNA sequence and pattern of expression

Substantial evidence has accumulated to suggest that in the near future implementation of the veto-cell-suppressor concept in the treatment of kidney allograft recipients might lead to the establishment of life-long specific allograft tolerance in the absence of further immunosuppressive therapy. Veto suppression prevents the generation of antigen-specific T-helper and cytotoxic T lymphocytes in vitro provided that the T-lymphocyte precursors specifically recognize antigenic peptides associated with the major histocompatibility complex molecules class II and class I, respectively, expressed on the surface of the veto-active cell. Data from a large number of experimental and clinical studies strongly indicate that veto-active cells function in vivo and are capable of preventing allograft rejection. Thus, donor-cell-mediated veto activity is the most likely explanation for the well-known graft tolerizing effect of pretransplant donor blood transfusions in kidney graft recipients. A prerequisite for a veto-active environment in vivo is the establishment of lymphoid microchimerism, in which veto-active donor and recipient cells mutually downregulate potential alloaggression.     

A new metal-binding site in photosynthetic bacterial reaction centers that modulates QA to QB electron transfer

Isolated reaction centers (RCs) from Rhodobacter sphaeroides were found to bind Zn(II) stoichiometrically and reversibly in addition to the 1 equiv of non-heme Fe(II). Metal and EPR analyses confirm that Zn(II) is ligated to a binding site that is distinct from the Fe site. When Zn(II) is bound to this site, electron transfer between the quinones QA and QB (QA-QB --> QAQB-) is slowed and the room-temperature kinetics become distributed across the microsecond to millisecond time domain. This effect of metal binding on the kinetics is similar to the more global effect of cooling RCs to 2 degreesC in the absence of Zn(II). This suggests that Zn(II) binding alters localized protein motions that are necessary for rapid QA-QB --> QAQB- electron transfer. Inspection of the RC crystal structure suggests a cluster of histidine ligands located beneath the QB binding pocket as a potential binding site.