Comprehensive analysis of nodal recurrence of advanced laryngeal carcinoma following surgery

The problems of nodal recurrence after surgical treatment of T3-4 laryngeal carcinoma were analysed. There were 133 N0 and 66 N+ patients. The 5-year actuarial nodal recurrence rate of N0 patients was 18% and N+ patients was 31%. Nodal recurrence was the commonest site of recurrence. The sites of nodal recurrence of N0 patients were at the level II, III, and IV nodes. Both ipsilateral and contralateral nodal recurrences were common. Of those patients who developed nodal recurrence, 63% patients were feasible for surgical salvage. Surgical salvage with radical neck dissection was the preferred treatment for nodal recurrence with 38% 5-year survival rate. The 'watchful waiting policy' in the management of N0 neck is an acceptable option with eventual nodal failure rate of 10% after surgical salvage. Close follow-up of patients is mandatory for the early detection of surgically salvageable nodal recurrence.

Critical appraisal of watchful waiting policy in the management of N0 neck of advanced laryngeal carcinoma

OBJECTIVE

To analyze the problem of nodal recurrence of N0 neck advanced laryngeal carcinoma.

DESIGN

Retrospective analysis.

SETTING

Hospital referral center.

PATIENTS

One hundred thirty-three patients with cancer stages T3-T4, N0, M0 who had total laryngectomy between January 1981 and December 1990.

MAIN OUTCOME MEASURE

Nodal recurrence.

RESULTS

Of the 11 patients who had elective radical neck dissections, there was no nodal recurrence. Of the other 122 patients who had no elective neck dissection, 19 patients (16%) developed nodal recurrence and all nodal recurrence was at levels II, III, and IV. Twelve patients (63%) underwent salvage radical neck dissection for nodal recurrence and they had a 38% adjusted 5-year actuarial survival rate. Of these 122 patients who had no elective neck dissection for the N0 neck, 12 patients (10%) eventually died of nodal recurrence.

CONCLUSIONS

The watchful waiting policy is a satisfactory management option of N0 neck of advanced laryngeal carcinoma.

GS28, a 28-kilodalton Golgi SNARE that participates in ER-Golgi transport

Little is known about the integral membrane proteins that participate in the early secretory pathway of mammalian cells. The complementary DNA encoding a 28-kilodalton protein (p28) of the cis-Golgi was cloned and sequenced. The protein was predicted to contain a central coiled-coil domain with a carboxyl-terminal membrane anchor. An in vitro assay for endoplasmic reticulum-Golgi transport was used to show that p28 participates in the docking and fusion stage of this transport event. Biochemical studies established that p28 is a core component of the Golgi SNAP receptor (SNARE) complex.

A study of patients' acceptance towards vaginal birth after caesarean section

Patients' acceptance towards vaginal birth after Caesarean section (VBAC) was studied in 99 women with previous Caesarean section. Their attitude was strongly related to the chance of success of VBAC. Only 53.3% of patients would accept VBAC if they were told that the chance of success was 70%. A history of vaginal delivery and a negative feeling towards previous operation were positively associated with acceptance of VBAC (p < 0.01), while convenience of elective Caesarean section and fear of vaginal delivery (even although most of them had had no vaginal delivery before) were the commonest reasons for refusal. The major caused of a negative feeling towards the previous Caesarean section were postoperative pain and a long recovery period. There was no significant negative effect on acceptance of VBAC if the previous Caesarean section was performed as an emergency operation for slow progress of labour or cephalopelvic disproportion.

The mammalian ARF-like protein 1 (Arl1) is associated with the Golgi complex

A rat cDNA clone was isolated which encodes a protein displaying characteristics of a ras-like small GTPase. The deduced amino acid sequence shows the highest amino acid identity (79%) with the Drosophila ARF-like protein 1 (dArl1) among all the known members of the ras-like small GTPase superfamily. The encoded protein was tentatively named rat Arl1 (rArl1). Northern blotting analysis revealed that the rArl1 gene is ubiquitously expressed in rat tissues. Recombinant rArl1 fused to glutathione-S-transferase (GST) to create GST-rArl1 binds GTP-gamma-S in a dose-dependent manner. Polyclonal antibodies raised against two unique rArl1 peptides recognized a 22 kDa protein in total NRK cell lysate. Immunofluorescence microscopy of NRK cells revealed discrete perinuclear labelling that could be competed out by GST-rArl1 but not GST. Examination of 8 additional cell lines revealed a similar labelling, suggesting that the antigen recognised by the antibodies is conserved and widely-expressed. Co-localization experiments in NRK cells with antibodies to mannosidase II and a newly identified cis-Golgi protein, p28, showed that rArl1 is localized to the Golgi complex. When cells were treated with nocodazole, the Golgi complex marked by mannosidase II and p28 was fragmented into punctate structures scattered throughout the cell, in which rArl1 was colocalized. Treatment with brefeldin A (BFA) resulted in the redistribution of rArl1 and mannosidase II into the cytoplasm and endoplasmic reticulum, respectively. The kinetics of the redistribution of rArl1 in response to BFA differ from those of ARF and beta-COP, two components of non-clathrin coated vesicles.

Retardation of a surface protein chimera at the cis Golgi

Dipeptidyl peptidase IV (D4) and the alpha subunit of human chorionic gonadotrophin (alpha hcg) are plasma membrane and secretory proteins, respectively. In the course of studies to understand mechanisms involved in transport along the exocytotic pathway, the ectoplasmic domain of D4 was replaced by the mature polypeptide of alpha hcg, resulting in the membrane anchored chimera, D4 alpha hcg. Surprisingly, when transfected into Chinese hamster ovary (CHO) and Madin-Darby canine kidney (MDCK) cells, strong perinuclear Golgi staining was predominant, in addition to the expected surface staining. By following the biogenesis and transport of the molecule, it was established that newly synthesized D4 alpha hdg is eventually transported to the cell surface but only after a significant retardation in the Golgi apparatus. The compartment of retardation was identified as the early or cis Golgi, before the medial Golgi, where resistance to endoglycosidase (endo) H is conferred. As a result of the transport retardation of the chimera, we were able to document the appearance of an endo D sensitive intermediate, which is usually too transient to be apparent in normal cells. The retardation of this chimera in the cis Golgi complements our previous report in which the D4 molecule with its transmembrane domain replaced by that of aminopeptidase N resulted in retardation in the trans Golgi/trans Golgi network in MDCK and CHO cells [Low, S. H., Tang, B. L., Wong, S. H., & Hong, W. (1994) J. Biol. Chem. 269, 1985-1994).(ABSTRACT TRUNCATED AT 250 WORDS)

Cell type differences in Golgi retention signals for transmembrane proteins

The transmembrane domain of Golgi resident proteins such as beta-galactoside alpha 2,6-sialyltransferase (ST) and N-acetylglucosaminyltransferase 1 (NT) contain a Golgi retention signal which confers Golgi retention to reporter proteins appended to them in the appropriate context. Thus, chimeras of the cell surface protein dipeptidyl peptidase IV containing the transmembrane domain of ST and NT are retained in the Golgi apparatus in MDCK and COS cells, as assessed by indirect immunofluorescence microscopy. Transfection of these chimeric constructs into CHO cells, however, results in their transport to vesicular structures which do not colocalize with that of an endogenous Golgi marker, mannosidase II. Furthermore, the staining pattern of these structures are not affected by brefeldin A. Biochemical analysis of the transgene products in pulse-chase experiments revealed that the chimeric proteins eventually become resistant to endoglycosidase H, suggesting that they are transported beyond the medial Golgi and therefore the vesicular structures are likely to be post-Golgi. The vesicular structures colocalized well with a lysosomal marker, cathepsin D, and also with internalized FITC-dextran chased into the lysosomal compartment. Monitoring the cell surface appearance of the chimeric protein suggests that the majority is transported directly to the lysosomal compartment. Golgi retention can be completely restored for ST and improved for NT by the inclusion of sequences flanking the transmembrane domain. Our results reflect cell type differences in the interpretation of the transmembrane domain Golgi retention signal, established that general Golgi retention of type II glycosyltransferases requires the hydrophilic flanking sequence as well as the transmembrane domain, and demonstrate that proteins which escape Golgi retention may be channeled to the lysosomal pathway.

Localization of the Lys, Asp, Glu, Leu tetrapeptide receptor to the Golgi complex and the intermediate compartment in mammalian cells

The carboxyl-terminal Lys-Asp-Glu-Leu (KDEL), or a closely-related sequence, is important for ER localization of both lumenal as well as type II membrane proteins. This sequence functions as a retrieval signal at post-ER compartment(s), but the exact compartment(s) where the retrieval occurs remains unresolved. With an affinity-purified antibody against the carboxyl-terminal sequence of the mammalian KDEL receptor, we have investigated its subcellular localization using immunogold labeling on thawed cryosections of different tissues, such as mouse spermatids and rat pancreas, as well as HeLa, Vero, NRK, and mouse L cells. We show that rab1 is an excellent marker of the intermediate compartment, and we use this marker, as well as budding profiles of the mouse hepatitis virus (MHV) in cells infected with this virus, to identify this compartment. Our results demonstrate that the KDEL receptor is concentrated in the intermediate compartment, as well as in the Golgi stack. Lower but significant labeling was detected in the rough ER. In general, only small amounts of the receptor were detected on the trans side of the Golgi stack, including the trans-Golgi network (TGN) of normal cells and tissues. However, some stress conditions, such as infection with vaccinia virus or vesicular stomatitis virus, as well as 20 degrees C or 43 degrees C treatment, resulted in a significant shift of the distribution towards the trans-TGN side of the Golgi stack. This shift could be quantified in HeLa cells stably expressing a TGN marker. No significant labeling was detected in structures distal to the TGN under all conditions tested. After GTP gamma S treatment of permeabilized cells, the receptor was detected in the beta-COP-containing buds/vesicles that accumulate after this treatment, suggesting that these vesicles may transport the receptor between compartments. We propose that retrieval of KDEL-containing proteins occurs at multiple post-ER compartments up to the TGN along the exocytotic pathway, and that within this pathway, the amounts of the receptor in different compartments varies according to physiological conditions.

Cytosolic factors block antibody binding to the C-terminal cytoplasmic tail of the KDEL receptor

The mammalian KDEL receptor is an extremely hydrophobic membrane protein. One of the longest stretches of hydrophilic sequence resides at the C-terminus. Various antibodies against a synthetic peptide corresponding to this region confirmed that the C-terminus is exposed to the cytoplasm. It was observed that antibody binding to the C-terminus of the KDEL receptor was diminished during immunofluorescence microscopy procedures which involved fixation prior to permeabilization as compared to when cells were permeabilized before fixation. Binding of both polyclonal and monoclonal antibodies, as assessed by indirect immunofluorescence microscopy in digitonin permeabilized cells, was inhibited by preincubation with rat liver cytosol. This inhibition was not observed with antibody against another membrane protein (p28) with a cytoplasmically exposed epitope also residing in the Golgi/intermediate compartment. Rabbit reticulocyte lysate had a similar effect while Schizosaccharomyces pombe cytosol inhibited binding to a greater degree than Saccharomyces cerevisiae cytosol. This inhibition by cytosol was prevented by coincubation with the antibody and was dose-dependent on the cytosol. Inhibition did not occur on ice or at 15 degrees C, or when the cytosol was energy-depleted by apyrase treatment. Interestingly, pretreatment of permeabilized cells with N-ethylmaleimide or its addition into the incubation mixture abolished inhibition. N-ethylmaleimide-treated cytosol, however, remained inhibitory. The findings suggest the existence of cytosolic factor (s) which interacts specifically with the cytoplasmic C-terminus of the KDEL receptor, which are likely to be components of the KDEL protein retrieval machinery.

Determination of fluvoxamine concentration in plasma by reversed-phase liquid chromatography

Fluvoxamine, a serotonin re-uptake inhibitor, was quantified in plasma by modifying a previously published procedure for monitoring plasma concentrations of tricyclic antidepressants. Alkalinized plasma samples were extracted with n-hexane/isoamyl alcohol, followed by back-extraction with diluted phosphoric acid. The extracts were analysed by reversed-phase liquid chromatography using a C-18 column, with phosphate/acetonitrile as the mobile phase. The assay was linear from 10 to 800 micrograms/L. Precision studies showed within-run and day-to-day coefficients of variation to be 4.5 and 6.8%, respectively. Desipramine interfered with the detection of fluvoxamine. The assay was used to measure a total of 8 plasma samples from 4 alcohol-dependent patients medicated with fluvoxamine as an adjunct to relapse prevention psychotherapy. In these patients, the plasma concentrations ranged from 54 to 241 micrograms/L. Dosage of fluvoxamine, duration of treatment, interval between last dosage and blood collection were associated with effects on plasma concentrations that were consistent with the pharmacokinetic profile of fluvoxamine.

Overexpression of E2F-1 in rat embryo fibroblasts leads to neoplastic transformation

The transcription factor E2F has been implicated in controlling the activation of multiple genes associated with cell proliferation. E2F-1, which is a component of E2F, can promote oncogenesis when transfected into REF cells. The transformation caused by E2F-1 correlates with constitutive overexpression of the transgene, increased transcription of E2F-dependent genes and the enhancement of two E2F DNA binding complexes containing the retinoblastoma susceptibility gene product (Rb) and E2F-1. The oncogenic potential of E2F-1 is dependent on functional DNA binding and transactivation domains but does not require the ability to interact directly with Rb. These findings provide the first direct evidence that sustained unregulated expression of E2F-1 can lead to the loss of cell proliferation control and that E2F-1 is a key component in cell cycle control.

Vogt-Koyanagi-Harada syndrome complicating allogeneic bone marrow transplantation

Vogt-Koyanagi-Harada (VKH) syndrome is an uncommon acute ophthalmological disorder, characterised by bilateral serous retinal detachment with diffuse choroiditis, in association with specific extra-ocular manifestations. We describe a patient with unequivocal VKH syndrome arising 49 days after matched unrelated donor bone marrow transplantation (BMT) performed as treatment for severe aplastic anaemia. The visual symptoms and retinal changes responded well to corticosteroids. The haematological relevance of VKH syndrome is to distinguish it from retinitis due to cytomegalovirus, which requires different therapy and has a far worse visual prognosis.

Golgi retardation in Madin-Darby canine kidney and Chinese hamster ovary cells of a transmembrane chimera of two surface proteins

Dipeptidyl peptidase IV (DDD) is a type II plasma membrane protein. Replacement of its transmembrane domain with that of another surface protein, aminopeptidase N, resulted in accumulation in the Golgi apparatus of Madin-Darby canine kidney cells and a delayed Golgi to surface transport in Chinese hamster ovary (CHO) cells. The compartment of retardation was identified as post medial-Golgi, most likely to be the trans-Golgi/trans Golgi network (TGN). Compared to native DDD, the rate of endoplasmic reticulum to Golgi transport for the chimera was largely unchanged in both cell types. On the other hand, Golgi to surface transport was delayed by more than 2 h in CHO cells and essentially undetectable up to 22 h of chase in Madin-Darby canine kidney cells. The decrease in the rate of Golgi to surface transport in CHO cells resulted in a significant accumulation of the fusion protein in the trans-Golgi/TGN. This phenomena is very unlikely to be due to any drastic conformational changes, as neither the enzyme activity nor the dimerization of the constructed molecule was affected. The findings of this study indicate that the transmembrane domain, in the context of its flanking sequences, is important for efficient Golgi to cell surface transport.

Effects of NH4Cl and nocodazole on polarized fibronectin secretion vary amongst different epithelial cell types

The extracellular matrix protein fibronectin was found to be secreted by three polarized epithelial cell lines Madin-Darby canine kidney (MDCK), Caco-2 and LLC-PK1. About 54 and 46% of fibronectin was secreted from the apical and basolateral cell surfaces, respectively, in MDCK cells. In Caco-2 and LLC-PK1 cells, the majority (about 92-93%) of fibronectin secretion occurs from the basolateral cell surface, with the remaining 7-8% from the apical surface. In all three cell types, NH4Cl was found to inhibit basolateral secretion (resulting in enhanced apical secretion), while total fibronectin secretion was not significantly affected (although a delay in secretion was observed). Nocodazole reduced total fibronectin secretion to about 70% of control levels in MDCK and Caco-2 cells, with significant inhibition on secretion from both surfaces. In contrast, total fibronectin secretion was enhanced by nocodazole in LLC-PK1 cells. Furthermore, the majority of fibronectin secretion was redirected to the apical cell surface in LLC-PK1 cells. These observations demonstrate that the nature as well as the extent of the effects of NH4-Cl and nocodazole on polarized fibronectin secretion varies amongst different epithelial cell types.

Advances in chromatography for clinical drug analysis: supercritical fluid chromatography, capillary electrophoresis, and selected high-performance liquid chromatography techniques

Advances have been made in chromatography complement immunoassay for clinical drug analysis. Chromatographic theory shows that the minimum detectable mass is directly proportional to the square of column radius. Small internal diameter columns are capable of analyzing lower analyte concentrations, and high resolution is achievable in open capillary columns, concomitant with greatly reduced mobile phase consumption and waste. This review, based on the author's experience and literature, focuses on supercritical fluid chromatography (SFC), capillary electrophoresis (CE), and selected high-performance liquid chromatography (HPLC) methodologies--microbore and direct-sample analysis (DSA) using commercially available Restricted Access Media (RAM) and REMEDi. In investigating the feasibility of SFC, the "normal-phase-like" selectivity of carbon dioxide was established, affecting the design of the extraction protocol and the elution order of drugs and metabolites. For example, the "more polar" tautomer eluted after FK-506, opposite to the order in the reversed-phase HPLC analysis. CE was investigated by Shihabi et al. for the analysis of pentobarbital and iohexol, while Evenson and Wiktorowicz performed preliminary evaluation of several therapeutic drug monitoring (TDM) drug groups. Innovation in HPLC column technology and hardware have greatly enhanced clinical drug analysis. Microbore column, offering enhanced mass sensitivity and high resolution, utilizes small sample size of 5 microliters of serum for the analysis of chloramphenicol. Commercially available RAM include internal surface reversed phase, shielded hydrophobic phase, and dual zone media, readily applicable for serum drug analysis without any sample preparation. Recently, an automated HPLC REMEDi offers urine and serum drug screening for toxicology.

The SXYQRL sequence in the cytoplasmic domain of TGN38 plays a major role in trans-Golgi network localization

The trans-Golgi network (TGN) plays a central role in protein sorting/targeting. TGN38 is an integral membrane protein confined mainly to the TGN. When the cytoplasmic 32-residue sequence of TGN38 was fused to the ecto- and transmembrane domains of glycophorin A (a surface protein), the resulting chimeric protein was localized to the TGN. Detailed mutagenesis of the 32-residue sequence revealed that the Ser, Tyr, and Leu residues at positions 23, 25, and 28, respectively, are essential for TGN localization. Further studies demonstrate that the sequence SXYQRL can by itself confer significant TGN localization.

Transmembrane topology of the mammalian KDEL receptor

The mammalian KDEL receptor is an integral membrane protein with seven hydrophobic regions. Fusion proteins comprising a 37-kDa N-glycosylation reporter fused downstream of amino-terminal fragments of the KDEL receptor with varying numbers of hydrophobic regions were synthesized in an in vitro translation system containing canine pancreatic microsomes. The luminal or cytosolic orientation of the reporter, and hence of the hydrophilic region to which it is fused, was inferred from the presence or absence of glycosylation, which occurs only in the lumen of the microsomes. The cytosolic orientation of the N and C termini was also confirmed immunocytochemically. Our results suggest that the KDEL receptor is inserted into the membrane with only six transmembrane domains and that both the amino and carboxy termini are located in the cytoplasm.

Evaluation of the triage system for emergency drugs-of-abuse testing in urine

The Triage Panel for Drugs of Abuse (DOA) was evaluated for detection of phencyclidine (PCP), amphetamines (AMPH), opiates (OPI), tetrahydrocannabinol (THC), the cocaine metabolite benzoylecgonine (BE), and barbiturates (BARB) in urine. This assay was compared with Syva EMIT. The comparisons were conducted on 606 positive and 325 negative samples. When there was a sufficient volume of sample available for retesting, positive and negative samples with discordant results between these two screening assays were confirmed by quantitative gas chromatography/mass spectrometry (GC/MS). The percent agreement between the two assays for positive samples ranged from 93 to 100%. For negative samples, the agreement ranged from 95 to 100%. For AMPH, 19 out of 27 discordant samples of urine that were positive for EMIT and negative for Triage DOA contained total amphetamine and methamphetamine concentrations of less than 1000 ng/mL by GC/MS. For THC, seven urine samples that were negative for Triage DOA and positive for EMIT contained 9-carboxy THC concentrations at greater than 15 ng/mL by GC/MS. For BARB, three samples that were negative for Triage DOA and positive for EMIT contained barbiturates levels greater than 300 ng/mL. Two of these three samples contained phenobarbital below the concentration that produces a positive result for Triage DOA. For the majority of the urine samples studied, however, the Triage DOA produced identical results to a commercial-instrument-based immunoassay.

Molecular cloning, characterization, subcellular localization and dynamics of p23, the mammalian KDEL receptor

We have isolated a cDNA clone (mERD2) for the mammalian (bovine) homologue of the yeast ERD2 gene, which codes for the yeast HDEL receptor. The deduced amino acid sequence bears extensive homology to its yeast counterpart and is almost identical to a previously described human sequence. The sequence predicts a very hydrophobic protein with multiple membrane spanning domains, as confirmed by analysis of the in vitro translation product. The protein encoded by mERD2 (p23) has widespread occurrence, being present in all the cell types examined. p23 was localized to the cis-side of the Golgi apparatus and to a spotty intermediate compartment which mediates ER to Golgi transport. A majority of the intracellular staining could be accumulated in the intermediate compartment by a low temperature (15 degrees C) or brefeldin A. During recovery from these treatments, the spotty intermediate compartment staining of p23 was shifted to the perinuclear staining of the Golgi apparatus and tubular structures marked by p23 were observed. These tubular structures may serve to mediate transport between the intermediate compartment and the Golgi apparatus.

An evaluation of the staphylococcal co-agglutination test for the detection of group A rotavirus in human faeces

The group A rotavirus staphylococcal co-agglutination test was evaluated and its sensitivity and specificity compared with an in-house enzyme-linked immunosorbent assay (ELISA) and a commercial latex agglutination test (Rotalex). In addition, the storage stability of the staphylococcal reagents was ascertained. Examination of 136 clarified suspensions of diarrhoeal faeces by the staphylococcal co-agglutination test revealed a high proportion of false positives (26%) and uninterpretable results (34%) due to non-specific agglutination. Non-specific agglutination could be removed effectively by prior absorption of the clarified faecal specimens with unsensitized staphylococci. The staphylococcal co-agglutination test was less sensitive and specific than the in-house enzyme-linked immunosorbent assay but was comparable to the Rotalex slide latex agglutination test. The staphylococcal reagents have a shelf life of at least 29 weeks.

Selective inhibition of protein targeting to the apical domain of MDCK cells by brefeldin A

Dipeptidyl peptidase IV (DPPIV) is mainly vectorially targeted to the apical surface in MDCK cells. BFA was found to abolish the apical targeting of DPPIV. This BFA effect could be achieved under conditions where the ER to Golgi transport and the total surface expression of DPPIV were essentially unaffected. BFA executed its effect during the transport from the trans-Golgi network (TGN) to the surface. The inhibition of apical targeting resulted in enhanced mis-targeting to the basolateral surface. The mistargeted DPPIV was transcytosed back to the apical domain only after BFA withdrawal. In contrast, the basolateral targeting of uvomorulin was unaffected by BFA. These results established that the apical targeting of DPPIV was selectively abolished by BFA.

Biochemical fractionation and characterization of proteins from Golgi-enriched membranes

Fractions enriched in Golgi membranes were prepared from rat liver by sucrose gradient ultracentrifugation. These enriched membranes were further subfractionated on the basis of their solubilities in EGTA, 150 mM sodium carbonate, pH 11.5, sodium deoxycholate, Triton X-100, or sodium dodecyl sulfate. This led to isolation of peripheral, luminal, and integral membrane proteins of the Golgi-enriched membranes. Luminal and membrane proteins were further purified by wheat germ agglutinin and concanavalin A lectin affinity chromatographies. Some proteins from these lectin columns were resolved by preparative gel electrophoresis and microsequenced. Subsequently, antibodies were produced for two proteins by immunization of either mice or rabbits. Immunofluorescence microscopy suggests that these proteins are confined to Golgi apparatus-like structures. The protocol described is well suited for the study of organelle structure and function.

The transmembrane domain of N-glucosaminyltransferase I contains a Golgi retention signal

The enzyme N-acetylglucosaminyltransferase I (NT, EC 2.4.1.101) is a resident type II transmembrane protein of the Golgi apparatus. To delineate the portion of its primary sequence that is responsible for the Golgi retention of this protein, we constructed chimeras containing different N-terminal portions of NT joined to a reporter sequence, the ectodomain of a type II surface membrane protein. These chimeric proteins were found to be retained in the Golgi apparatus as assessed by cell surface biotinylation and immunofluorescence. We found that the transmembrane domain of NT is sufficient to confer Golgi retention of the fusion proteins and propose that it contains the Golgi retention signal of the parent molecule.

Retention of a type II surface membrane protein in the endoplasmic reticulum by the Lys-Asp-Glu-Leu sequence

Soluble luminal proteins of the endoplasmic reticulum (ER) are known to be retained by a tetrapeptide retention signal, KDEL. We report in this communication that the KDEL sequence when appended to the carboxy terminus of a cell surface membrane protein, dipeptidyl peptidase IV (DPPIV), resulted in its retention in the endoplasmic reticulum of transfected Madin-Darby canine kidney cells as assessed by indirect immunofluorescence. Selective surface biotinylation revealed that about 90-95% of the expressed DPPIV was retained in the ER. Appendance of the sequence KDEV did not, however, result in ER retention, illustrating the functional specificity of the retention signal. The ER retention was not due to misfolding of the mutant protein, as the mutant proteins remained enzymatically active. Our data suggest that the KDEL receptor is able to recognize and recycle type II membrane proteins containing a carboxyl-terminal KDEL sequence and postulates the existence of such yet to be identified endogenous proteins.

The 17-residue transmembrane domain of beta-galactoside alpha 2,6-sialyltransferase is sufficient for Golgi retention

beta-Galactoside alpha 2,6-sialyltransferase (ST) is a type II integral membrane protein of the Golgi apparatus involved in the sialylation of N-linked glycans. A series of experiments has shown that the 17-residue transmembrane domain of ST is sufficient to confer localization to the Golgi apparatus when transferred to the corresponding region of a cell surface type II integral membrane protein. Lectin affinity chromatography of chimeric proteins bearing this 17-residue sequence suggests that these chimeric proteins are localized in the trans-Golgi cisternae and/or trans-Golgi network. Further experiments suggest that this 17-residue sequence functions as a retention signal for the Golgi apparatus.

Disturbances in the composition of plasma lipoproteins during gram-negative sepsis in the rat

Hyperlipidemia is associated with gram-negative sepsis. In this study we characterized the plasma lipoproteins of fasted and fed septic and control rats with respect to their lipid and apolipoprotein composition. Sepsis was induced by i.v. injection of 8 x 10(7) live Escherichia coli colonies/100 g body wt. Food was removed from fasted control and fasted E. coli-treated rats after injection. Fed rats were infused intragastrically with a nutritionally complete diet for 5 days prior to E. coli treatment. 24 h after treatment with E. coli, lipid and protein concentrations of very-low-density lipoprotein (VLDL) were over 2-fold higher in the fasted E. coli-treated rats than those of the fasted control rats. This appears to be due to a decrease in the clearance of VLDL. The relative composition of apolipoprotein B-48 and apolipoprotein E were lower while that of apolipoprotein B-100 was higher in fasted E. coli-treated rats than in fasted controls. Low-density lipoprotein (LDL) and high-density lipoprotein lipids were also significantly elevated, indicating greater synthesis of these particles during sepsis and food deprivation. By contrast, VLDL-triacyglycerol from fed, E. coli-treated did not differ from that of their respective controls although the total cholesterol remained elevated. Percentages of apolipoprotein B-48 and apolipoprotein B-100 increased while apolipoprotein E contributed significantly less to the total protein of VLDL from the E. coli-treated rats compared with controls. LDL lipids were also increased. In conclusion, gram-negative sepsis leads to marked changes in the plasma lipoprotein composition which may be attributed to altered hepatic synthesis, peripheral metabolism or hepatic uptake of lipoproteins and their remnants. These in turn may be a function of the nutritional status.

Nitrous oxide and internal tamponade during vitrectomy

We analysed the nitrous oxide composition of the intraocular gas bubble following vitrectomy and fluid-air exchange in 12 patients. Samples were taken under standardised conditions at 20 minutes after completion of the fluid-air exchange. Analysis was conducted by a Medishield MS2 mass spectrometer. The percentage composition of nitrous oxide in the samples varied between 4 and 21% (mean 9%). This influx of nitrous oxide was associated with an increase of intraocular pressure. Pressure rises of greater than 20 mm Hg were not seen owing to venting of gas through the sclerostomies. An inverse relationship was noted between the extent of retinal detachment preoperatively and the amount of nitrous oxide entering the eye. A possible explanation for this relationship is proposed. The importance of nitrous oxide movement is stressed.

Involvement of both vectorial and transcytotic pathways in the preferential apical cell surface localization of rat dipeptidyl peptidase IV in transfected LLC-PK1 cells

Dipeptidyl peptidase IV (DPPIV) is a membrane glycoprotein with type II orientation. It is predominantly localized to the apical surface in epithelial cells. Previous studies (Bantles, J. P., Feracci, H. M., Shinger, B., and Hubbard, A. L. (1987) J. Cell Biol. 105, 1241-1251) using cellular fractionation and immunoprecipitation in rat liver suggest that DPPIV is targeted to the apical surface by an indirect pathway through transient appearance in the basolateral surface followed by specific transcytosis to the apical domain. In transfected Madin-Darby canine kidney (MDCK) cells using domain-selective biotinylation and streptavidin absorption, it was, however, shown that DPPIV is directly sorted to the apical surface (Low, S. H., Wong, S. H., Tang, B. L. Subramaniam, V. N., and Hong, W. (1991) J. Biol. Chem, 266, 13391-13396). These studies suggest that the sorting pathway for DPPIV may be cell type-specific, but it cannot be ruled out that the observed difference in the DPPIV sorting pathway may be due to different methods employed for dissecting the sorting pathway. In this study, we have expressed rat DPPIV, using an expression system driven by the Rous sarcoma virus enhancer and the SV40 early promoter region, in another epithelial cell line, LLC-PK1. As in MDCK cells, DPPIV is preferentially (about 90%) localized to the apical surface. Employing identical methods used previously in MDCK cells, it was found that both direct and transcytotic pathways are involved in the apical surface localization of DPPIV in this epithelial cell type. These observations clearly illustrate that the sorting pathway of rat DPPIV is cell type-specific.

Inhibition by brefeldin A of protein secretion from the apical cell surface of Madin-Darby canine kidney cells

The effect of brefeldin A (BFA) on total and polarized protein secretion was examined in MDCK cells. Increasing concentrations of BFA have increasingly inhibitory effects on total protein secretion. The total protein secretion was essentially unaffected by BFA at 0.5 microgram/ml. When the BFA concentration was increased to 10 and 30 micrograms/ml, the total protein secretion was reduced to about 70 and 25%, respectively, of the control level. Consistent with this effect on total protein secretion, the Golgi structure as revealed by C6-NBD-ceramide (a fluorescent ceramide analog) staining was essentially unaltered by 0.5 microgram/ml BFA, while 10 and 30 micrograms/ml BFA significantly dispersed the Golgi apparatus. When the polarity of protein secretion was examined, it was found that the ratio of proteins secreted from the apical to those from the basolateral surface was reduced from 1.5-2.0 to 0.4-0.7 by all three BFA concentrations. Furthermore, several proteins which are preferentially released from the apical surface were found to be released without apparent surface polarity, while several other proteins which were preferentially released from the basolateral surface were unaffected. This study suggests that BFA, at 0.5 microgram/ml, can selectively inhibit protein secretion from the apical surface without affecting total protein secretion. The inhibition of apical secretion results in enhanced protein secretion from the basolateral surface.

Apical cell surface expression of rat dipeptidyl peptidase IV in transfected Madin-Darby canine kidney cells

Dipeptidyl peptidase IV (DPPIV) is a type II membrane glycoprotein that is predominantly localized to the apical plasma membrane in various epithelial cells. In order to understand in more detail the biogenesis and sorting of DPPIV, the cDNA for rat DPPIV was inserted into a mammalian plasmid expression vector so that DPPIV expression was driven by a control region composed of the SV40 early promoter region fused to the enhancer of the Rous sarcoma virus. Madin-Darby canine kidney cells transfected with this construct were found to express the DPPIV protein. In these transfected cells, the majority of DPPIV was present on the apial cell surface. This observation suggests that the information for apical surface localization is inherent in the DPPIV molecule itself and that this sorting information is decipherable in the epithelial cells of a different species. DPPIV is transported efficiently from the endoplasmic reticulum to the Golgi apparatus as assessed by pulse-chase experiments. Furthermore, evidence is presented which suggests that the majority of DPPIV is sorted intracellularly to the apical cell surface. The same protein has, however, been reported to be sorted by an indirect pathway through transcytosis from the basolateral to the apical cell surface in hepatocytes (Bartles, J.R., Feracci, H., M., Stinger, B., and Hubbard, A.L. (1987) J. Cell Biol. 105, 1241-1251). This study suggests that the same protein can take two different pathways in different cell types for its correct apical cell surface localization.

Calcium and ethanol-induced gastric mucosal damage in rats

The effects of graded doses of ethanol on stomach mucosal damage and calcium levels were studied in rats. The influence of verapamil and/or calcium chloride on these changes was also investigated. Orally administered ethanol (20, 50 or 80% v/v) markedly decreased gastric glandular tissue calcium and it concentration dependently produced mucosal lesions. Pretreatment with verapamil (2.5 or 5 mg/kg, i.p.) dose dependently lessened glandular wall calcium levels and worsened ethanol-induced mucosal damage. Calcium chloride (50 mg/kg, i.p.) significantly prevented ethanol-induced gastric calcium depletion; it also dose dependently antagonized the damaging effect of ethanol as well as the lesion-intensifying action of verapamil. The findings that verapamil potentiated, whereas calcium chloride prevented, ethanol-induced glandular mucosal damage and tissue calcium changes indeed suggest that altered gastric cell calcium levels could be closely related to the mucosal lesions produced by ethanol in rats.

Determination of fluoxetine and norfluoxetine by high-performance liquid chromatography

A high-performance liquid chromatographic assay was developed for a recently introduced atypical antidepressant, fluoxetine and its demethylated metabolite, norfluoxetine. Prior to analysis, aliquots of alkalinized plasma were extracted with n-hexane and isoamyl alcohol, followed by back-extraction with diluted phosphoric acid. These extracts were injected into a 10 microns, reversed-phase C18 column with phosphate and acetonitrile as the mobile phase and detection at 214 nm. Peak height ratios were linearly correlated up to 800 micrograms/l. Acceptable coefficients of variation were demonstrated for both within-run and day-to-day studies. Selected drugs were checked for interference. The assay was used to monitor nine patients receiving 20 to 80 mg of fluoxetine per day. Plasma concentrations of fluoxetine and norfluoxetine ranged from 37 to 301 micrograms/l and 29 to 326 micrograms/l respectively.

Novel strategies for clinical drug analysis with new column technology in liquid chromatography

Clinical drug analysis has been the focus of much attention and controversy because of the increase in substance abuse testing of addicts, patients, employees and others, in addition to the rapidly growing fields of therapeutic drug monitoring and clinical toxicology. This review focuses on the latest methodological and technological advances in liquid chromatography (LC) as it is applied to clinical drug analysis. Based on the author's experience, key chromatographic parameters such as carbon load, functionalities and temperature are proposed for the separation of structurally similar metabolites and for resolving chromatographic interferences by other drugs and metabolites. Novel sample preparation for cyclosporine and gradient elution of its metabolites are reviewed, followed by an update on monitoring of 3'-azido-3'-deoxythymidine with emphasis on automated sample preparation. Various approaches of direct sample analysis are advocated for increased efficiency as a result of minimal sample preparation and potential advantages such as decreased exposure of personnel to infectious samples. An update of microbore LC indicates that 2-mm columns may be readily used for clinical paediatric and neonatal analysis without dedicated chromatographs. Potential applications of multidimensional-multimodal chromatography include analyses of a cocaine impurity, anticonvulsants, antidepressants, and five ingredients of a common cold medication.

The role of serotonin in ethanol-induced gastric glandular damage in rats

The effects of serotonin (5-HT) or methysergide (a 5-HT antagonist), given intraperitoneally 30 min beforehand, on ethanol-induced mucosal injury and mucosal blood flow were studied in rats. 5-HT itself dose dependently decreased the gastric mucosal mucus content and induced gastric damage in conscious animals. It also worsened ethanol-induced lesion formation but not mucus depletion. Methysergide pretreatment only prevented the former action. In the ex vivo chamber preparation, 5-HT lowered the gastric mucosal blood flow and produced mucosal damage in unconscious animals. It also potentiated ethanol-induced gastric injury and 5-HT release. Methysergide significantly prevented lesion formation and 5-HT release in ethanol-treated rats. Ethanol decreased the gastric mucosal blood flow in the mucosa which had been preincubated with HCl. This depression of gastric mucosal blood flow was further reduced by 5-HT, but was reversed by methysergide. The lesion-potentiating or -protecting actions of 5-HT or methysergide, respectively, suggest that the amine is involved in gastric mucosal damage by ethanol in rats.

Detection of lipid peroxidation in lung and in bronchoalveolar lavage cells and fluid

Inhalation of toxic materials such as asbestos, silica, 100% oxygen, ozone, or nitrogen dioxide may lead to an increased production of reactive oxygen metabolites which may initiate lipid peroxidation. Measurement of lipid peroxidation in cells and fluid obtained by bronchoalveolar lavage (BAL), as well as in lung tissue, may aid in monitoring the development and extent of pulmonary damage after inhalation of a toxic substance. In this study, we employed a sensitive assay for detection of malondialdehyde (MDA), a breakdown product of lipid peroxidation. By separation of the adduct with thiobarbituric acid, using a reverse phase high pressure liquid chromatographic technique, we accurately and sensitively measured the content of MDA in BAL cells, lavage fluid, and lavaged lung tissue homogenates of rats. The amounts of sample required for detection of MDA were small enough possibly to be applied to use with human specimens; in addition, recovery of added MDA was acceptable with all types of samples. Inclusion of a metal chelator in the preparation of samples appeared necessary to prevent metal-catalyzed propagation of lipid peroxidation during the assay. Overall, the method described here using samples from rats may be applicable to detecting lipid peroxidation in BAL samples from humans.

Effects of eicosapentaenoic and docosahexaenoic acids on apoprotein B mRNA and secretion of very low density lipoprotein in HepG2 cells

Oleic acid (18:1n-9, OA), docosahexaenoic acid (22:6n-3, DHA), or eicosapentaenoic acid (20:5n-3, EPA) was added to HepG2 cells at a concentration of 1 mM in a 5:1 or 2:1 molar complex with bovine serum albumin (BSA), and this was incubated for 3 hours. The incorporation of 3H-glycerol into cellular and medium triglyceride (TG), and the mass of TG were measured. The effects of these fatty acids on the secretion of very low density lipoprotein (VLDL) apolipoprotein B (apo B) were estimated from the incorporation of 3H-leucine into the medium apo B in comparison to cells incubated with fatty acid-poor albumin. The secretion of human albumin by the cells was also estimated by immunochemical precipitation of the labeled albumin. In addition, the intracellular levels of apo B messenger ribonucleic acid (mRNA) were measured by the dot-blot hybridization technique. Relative to control cells incubated with BSA, OA (complexed to BSA at a 5:1 molar ratio) stimulated TG synthesis and secretion sevenfold. Compared to OA, EPA was 24% less effective for both processes, whereas DHA inhibited only the secretion of TG (-43%). The secretion of VLDL apo B was not affected by OA, but was decreased 31% by EPA and 54% by DHA. When the molar ratio of fatty acid complexed to albumin was changed to 2:1, similar results were obtained with respect to TG production. The levels of apo B mRNA relative to actin mRNA were not significantly altered by any of the fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicity to alveolar macrophages in rats following parenteral injection of nickel chloride

Alveolar macrophages collected by pulmonary lavage from male Fischer-344 rats at intervals (1-72 hr) after NiCl2 injection (62-500 mumol/kg, sc) were tested by several techniques. Within 1 to 4 hr, the macrophages showed morphological and biochemical signs of activation (hypertrophy, ruffled plasma membrane, increased cyclic AMP concentration, and markedly diminished 5'-nucleotidase activity, assayed by concanavalin A inhibition). Functional impairment (reduced phagocytic activity) was first seen at 24 hr; lipid peroxidation (increased malondialdehyde concentration) was not detected until 48 hr. Dose- and time-related effects of NiCl2 on 5'-nucleotidase activity, phagocytic activity, malondialdehyde concentration, and nickel content of alveolar macrophages were observed 24 to 72 hr postinjection. Diminished cell viability occurred only at 72 hr after the highest dosage of NiCl2. In alveolar macrophages from 63NiCl2-treated rats, 63Ni was located primarily in the cytoplasm, based upon liquid scintillation counting and autoradiography; fractionations of macrophage cytosol by gel filtration chromatography showed that 63Ni was bound to several high- and low-molecular-weight constituents. This study demonstrates that sc administration of NiCl2 to rats caused nickel uptake into and activation of alveolar macrophages, followed by reduced phagocytic capacity. The alveolar macrophage was a cellular target for nickel toxicity following parenteral exposure to NiCl2.

Supercritical fluid chromatography and microbore liquid chromatography for drug analysis

Supercritical fluid and microbore liquid chromatography offer potential applications for drug analysis. In supercritical fluid chromatography (SFC), the mobile phase is a gas (e.g., carbon dioxide) maintained at its supercritical state--that is, above its critical temperature and pressure, above which it cannot be liquefied even with further increases in applied pressure. The SFC mobile phase has low viscosity, approximating that of a gas, and high diffusivity, between those of a gas and a liquid. These properties yield favorable column efficiency, between that of capillary gas chromatography (GC) and liquid chromatography (LC). SFC analysis may be performed by either packed or open tubular capillary columns and with GC and LC detectors. SFC, interfaced with mass spectrometry, may become a viable alternative to GC/MS for drug identification in clinical and forensic toxicology. Advantages of microbore liquid chromatography include enhanced mass sensitivity, reduced solvent consumption, and others. Microbore columns (internal diameters 1 to 2 mm) may be packed with 3-, 5-, or 10-micron particles. Potential applications include micro-sample analysis (5-200 microL) for neonatal and pediatric drug monitoring, and drug confirmation analysis for toxicology.

Supercritical fluid chromatography and microbore liquid chromatography for drug analysis

Supercritical fluid and microbore liquid chromatography offer potential applications for drug analysis. In supercritical fluid chromatography (SFC), the mobile phase is a gas (e.g., carbon dioxide) maintained at its supercritical state--that is, above its critical temperature and pressure, above which it cannot be liquefied even with further increases in applied pressure. The SFC mobile phase has low viscosity, approximating that of a gas, and high diffusivity, between those of a gas and a liquid. These properties yield favorable column efficiency, between that of capillary gas chromatography (GC) and liquid chromatography (LC). SFC analysis may be performed by either packed or open tubular capillary columns and with GC and LC detectors. SFC, interfaced with mass spectrometry, may become a viable alternative to GC/MS for drug identification in clinical and forensic toxicology. Advantages of microbore liquid chromatography include enhanced mass sensitivity, reduced solvent consumption, and others. Microbore columns (internal diameters 1 to 2 mm) may be packed with 3-, 5-, or 10-micron particles. Potential applications include micro-sample analysis (5-200 microL) for neonatal and pediatric drug monitoring, and drug confirmation analysis for toxicology.

Advances in liquid chromatography and related methodologies for therapeutic drug monitoring

In this article the merits of current liquid chromatography (LC) columns and techniques are reviewed, to include the following topics: (1) a brief introduction to rational therapeutic drug monitoring (TDM) to justify drug measurements; (2) selected recent survey results from the College of American Pathologists (CAP) to establish the current utilization pattern of LC for TDM in the USA; (3) LC analyses of major classes of drugs--antiarrhythmics, antidepressants, antiepileptics, antimicrobials, cyclosporine, and others--with emphasis on analysis of these drugs in human serum or plasma, by focusing on the less usual, reversed-phase functional groups such as CN and phenyl, and by the use of "mini" columns, silica and polymeric columns, the emphasis being reduced on the well-established C-18 columns; (4) high-speed LC; (5) various approaches of direct sample analysis--solvent extraction, automated sample processing, column switching, micro-injections, micellar chromatography, electrochemical detection with photolytic derivation, and the internal surface reversed-phase column of Pinkerton; (6) microbore LC drug analysis; (7) clinical chiral separation; and (8) overall conclusions.

Inhibition of apolipoprotein secretion and phosphatidate phosphohydrolase activity by eicosapentaenoic and docosahexaenoic acids in the perfused rat liver

Infusion of albumin-bound eicosapentaenoic acid (EPA) docosahexaenoic acid (DHA), or oleic acid (OA) in perfused rat livers was carried out for two hours at a rate that maintained the perfusate concentration at 1 mmol/L. When compared with fatty acid-poor albumin alone, triacylglycerol (TAG) output was not significantly increased with DHA or EPA, whereas OA infusion resulted in a twofold increase. Incorporation of labeled leucine into VLDL apo B-100, apo B-48, apo E, and apo Cs was decreased by 50% by DHA or EPA compared with OA. The total phosphatidate phosphohydrolase activity was decreased by 35% with DHA or EPA compared to oleic acid or albumin alone. In no case was there a significant change in the distribution of activity between the microsomal and cytosolic factions. Fatty acid infusion did not significantly change the liver TAG content. Total liver lipids, microsomal lipids, and lipids of secreted VLDL were enriched with the infused fatty acids. The degree of enrichment for secreted TAG averaged 24% for OA and 36% for DHA or EPA. The effects of DHA and EPA on PPH activity and on apo B secretion in feeding experiments with marine oils rich in these acids may relate to changes in the fatty acid composition of liver membranes.

Measurement of antidepressants by liquid chromatography: a review of current methodology

Antidepressant measurement by liquid chromatography (LC) has enhanced the therapy of patients who are being treated with some of the first generation tricyclic antidepressants; the merits of routinely monitoring the other antidepressants await further study. Currently, the role of LC is changing from dominant to complementary as a result of the recent availability of monoclonal antibody immunoassays with increased specificity. For successful application of LC, considerations would include designing the sampling protocol and matching assay that together are uniquely suitable for a particular laboratory. The assay should be simple, the sample preparation manual (liquid-liquid, solid-phase extraction columns), semi-automated, or automated. Normal- or reversed-phase columns with functionalities such as C-18, CN, C-8, and phenyl are used. Other useful LC variables include particle size, capping, ion-pairing, and recycling. This survey of LC methods includes the first and second generations, and new antidepressants such as alprazolam, amoxapine, bupropion, maprotiline, trazodone, and selected metabolites. Potential chromatographic interference by (e.g.) benzodiazepines and neuroleptics is addressed, followed by proposed guidelines for their resolution. Future developments are discussed.

Measurement of antidepressants by liquid chromatography: a review of current methodology

Antidepressant measurement by liquid chromatography (LC) has enhanced the therapy of patients who are being treated with some of the first generation tricyclic antidepressants; the merits of routinely monitoring the other antidepressants await further study. Currently, the role of LC is changing from dominant to complementary as a result of the recent availability of monoclonal antibody immunoassays with increased specificity. For successful application of LC, considerations would include designing the sampling protocol and matching assay that together are uniquely suitable for a particular laboratory. The assay should be simple, the sample preparation manual (liquid-liquid, solid-phase extraction columns), semi-automated, or automated. Normal- or reversed-phase columns with functionalities such as C-18, CN, C-8, and phenyl are used. Other useful LC variables include particle size, capping, ion-pairing, and recycling. This survey of LC methods includes the first and second generations, and new antidepressants such as alprazolam, amoxapine, bupropion, maprotiline, trazodone, and selected metabolites. Potential chromatographic interference by (e.g.) benzodiazepines and neuroleptics is addressed, followed by proposed guidelines for their resolution. Future developments are discussed.

The influence of omeprazole on the protective effects of secretagogues against ethanol-induced gastric ulceration in rats

The influence of omeprazole on the antiulcer effects of histamine, methacholine and pentagastrin on ethanol-induced gastric ulceration was studied. Histamine 5 mg/kg, methacholine 500 micrograms/kg or pentagastrin 100 micrograms/kg pretreatment s.c. markedly reduced ethanol (50%, 10 ml/kg p.o.)-induced gastric ulceration in pylorus-ligated conscious rats, but significantly elevated the gastric secretory volume and acid output. Omeprazole pretreatment 50 mg/kg s.c. reduced gastric secretion and abolished the ulcer-protecting effects of the three secretagogues. The same doses of histamine, methacholine or pentagastrin did not significantly alter the gastric secretory volume but increased the total acid output of ex-vivo stomach chamber preparations in anaesthetised animals. Histamine worsened ethanol-evoked ulceration whereas methacholine and pentagastrin had no effect on the lesions. Omeprazole pretreatment did not prevent ulcer aggravation by histamine. It is concluded that the antiulcer effects of the three secretagogues in conscious animals are probably due to the increased secretory volume which lessens the ulcerogenic action of ethanol by its dilution. Omeprazole reduces the secretory volume and thus prevents the antiulcer effect of these secretagogues. The findings with histamine and omeprazole in the ex-vivo stomach experiments support the suggestion that it is unlikely that increased gastric acid secretion affects the ulcerogenicity of ethanol in rat stomach.

Preoperative and intraoperative localisation of gastrointestinal bleeding of obscure origin

In the past six years, 37 patients with gastrointestinal bleeding of obscure origin had their bleeding sites localised preoperatively or intraoperatively. Preoperative investigations followed a regime consisting of endoscopy, barium meal and follow through, small bowel enema, 99mTc pertechnetate scan, 99mTc-labelled red blood cell scan and selective coeliac and mesenteric angiography. Bleeding lesions were localised preoperatively in 36 patients. In one patient, diagnostic laparotomy had to be carried out immediately before any investigation because the bleeding was severe. At operation, angiosarcoma of ileum was found. Unless preoperative investigations showed the lesions to be in anatomically fixed organs like the duodenum or colon, the lesions had still to be found at operation. Palpation and transillumination detected the lesion intraoperatively in 21 patients while only some lesions were found in three patients with multiple lesions. Sigmoidoscopy through enterotomies was required in one patient. Intraoperative enteroscopy was done for small lesions not found grossly at operation in nine patients, to detect additional lesions in three patients or to rule out suspicious lesion shown on preoperative tests in one patient. In another patient with diffuse lymphoma of small bowel with bleeding from only a small segment of jejunum, injection of methylene blue intraoperatively through a previously placed angiographic catheter stained the bleeding segment of jejunum blue. This segment was identified easily and resected. These preoperative and intraoperative localisation procedures were simple and effective and we recommend them to be used more freely.

Methodologies for antidepressant monitoring

Advances in clinical analytic technology have contributed to antidepressant therapy. This article emphasizes recent developments in liquid chromatographic and immunoassays, including the "semiquantitative" and quantitative enzyme multiplied immunoassay technique (EMIT) and fluorescence polarization immunoassay (FPIA).

Acute thymic involution and increased lipoperoxides in thymus of nickel chloride-treated rats

Acute thymic involution occurred in male, Fischer-344 rats following a single injection of nickel chloride (0.5 mmol/kg, sc). In nickel-treated rats, the mean thymic weight became significantly decreased at 24 h, continued to diminish at 48 h, and reached 24% of the control value at 72 h post-injection. The ratio of thymic weight to body weight (mg/g) decreased from 1.24 +/- 0.05 (SD) in control rats to 0.30 +/- 0.05 in nickel-treated rats at 72 h post-injection (p less than 0.01). Concentrations of thymic lipoperoxides were assayed by the thiobarbituric acid reaction, with HPLC separation and spectrophotometric quantitation of the malondialdehyde-thiobarbituric acid complex. The mean concentration of thymic lipoperoxides was unchanged at 24 h, increased 2-fold at 48 h, and reached 8-times the control value at 72 h after nickel chloride injection. On histological examination, sections of thymus from nickel-treated rats showed moderate to profound depletion of cortical lymphocytes at 72 h post-injection. Marked degenerative changes were noted in cortical lymphocytes, with pyknosis and karyorrhexis; swelling and vacuolation were evident in thymic reticular epithelial cells. The time-courses of the biochemical and histopathological responses suggest that the lipid peroxidation may be an end-result, rather than a cause, of thymic involution and injury to thymic lymphocytes in nickel-treated rats.