Mass spectrometric identification of amino acid transformations during oxidation of peptides and proteins: modifications of methionine and tyrosine

Liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS), tandem mass spectrometry with on-line liquid chromatography (LC/ESI-MS/MS) and high-resolution mass spectrometry with liquid secondary ionization (LSI-MS) were utilized to identify the modified amino acids in peptides and proteins formed during oxidation with performic acid. The procedure of protein oxidation was chosen to assist in protein unfolding by oxidizing the cystines to cysteic acids to allow for more complete proteolytic digestion and to create additional cleavage sites for endoproteinase Asp-N. Investigation of the Asp-N peptide map of oxidized superoxide dismutase (SOD) by LC/ESI-MS revealed that an expected proteolytic fragment of the protein was missing. In its place, two peptides with molecular weights 66 and 100 higher than that calculated for the missing peptide were observed. To identify the modified amino acids in the unexpected peptides, a model peptide with some amino acid similarities (tyrosine, arginine, methionine, lysine) to the missing peptide was chosen and was subjected to similar oxidation and enzymatic digestion steps, conditions, and reactions. After oxidation and digestion, the model peptide (TAP; sequence, Ac-MDKVLNRY) showed three major peaks in LC/MS. The peptides in the three peaks were identified as the unmodified peptide and two peptides whose molecular weights were 66 and 100 higher than that of TAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Natural history study of hereditary multiple exostoses

Hereditary multiple exostosis (EXT) is an autosomal dominant disorder in which the clinical hallmark is the growth of bony protuberances from long bones and which can cause a variety of orthopedic deformities. This study sought to further delineate the natural history of EXT. In addition, since previous studies have suggested that there are deviations from Mendelian expectations in EXT, including incomplete penetrance and a skewed sex ratio, we attempted to confirm or refute these suggestions. Both portions of the study were carried out through retrospective review of 43 affected probands and 137 of their affected relatives. Data are presented concerning frequency and severity of complications of EXT including short stature, sequelae of exostoses, occurrence of malignant degeneration of exostoses, and problems in pregnancy and delivery of affected females. Only 2.8% of the total affected population had experienced exostosis-related malignancy, an estimate which is considerably less than earlier reports would suggest. Penetrance was 100%. There was an excess of males within the entire affected population (104:76) and within identified probands (28:15). However, the male to female ratio was unskewed in nuclear families (probands, affected sibs, and parents). The excess of males appears to be related to males having more severe and more frequent complications of EXT than having any primary genetic origin.

Evaluation of Angus, Charolais and Hereford as terminal sire breeds on Hereford and first-cross cows. I. Growth of progeny

Pre-weaning growth of 482 Angus, Charolais and Hereford sired progeny out of straightbred Hereford (H x H) , and first-cross Brahman x Hereford (B x H) , Simmental x Hereford (S x H) and Friesian x Hereford (F x H) dams was evaluated. The dams grazed either high, medium or low quality pasture (pre-weaning pasture system) at Grafton, NSW. Progeny of dams from high quality pre-weaning pasture were slaughtered at 281 days of age for the vealer market. The progeny of dams from medium and low quality pre-weaning pastures were evaluated for post-weaning growth on pasture, on commercial properties in temperate NSW. They were slaughtered for either the yearling domestic (both sexes) or heavy export steer markets. Average daily gain (ADG) for the entire pre-weaning period was greater (P < 0.05) for Charolais (845 g/day) than Angus (790 g/day) and Hereford (783 g/day) sired progeny. This resulted in a higher ( P < 0.05) weaning weight of Charolais sired progeny of dams on high or medium quality pre-weaning pasture. On low quality pasture, however, sire breed differences in weaning weight were not significant (P > 0.05). This indicates that adequate nutrition should be provided for Charolais sired progeny to express their higher growth potential. Post-weaning ADG of Charolais sired progeny was higher (P < 0.05) than that of Angus or Hereford sired progeny, resulting in 14 months liveweight (for yearling domestic cattle) of 370, 345 and 345 kg and 27 months liveweight (for heavy export steers) of 635, 585 and 569 kg for Charolais, Angus and Hereford sired progeny respectively. Progeny of B x H dams on medium or low quality pre-weaning pastures had the highest pre-weaning ADG and weaning weight, but the lowest post-weaning ADG. This resulted in 27 months liveweight of 558, 582, 628 and 616 kg for steer progeny from H x H, B x H, S x H and F x H dams respectively.

Occlusion and stability of synthetic femoral canal plugs used in cemented hip arthroplasty

The occlusion and stability of five synthetic plugs used to restrict the femoral canal prior to cemented arthroplasty was assessed. A model was employed consisting of a hollow wooden dowel to simulate the canal, with adapters fixed to both ends to accommodate cement insertion and pressurization, and to produce a closed distal cavity. Three different canal diameters within the range accommodated by the plug selected were employed to assess insertion force, distal pressure during both insertion and pressurization of acrylic cement, and plug migration and leakage for each device. There was a wide variation among plugs in the magnitudes of the force and distal pressure upon plug insertion. During cement pressurization, cement leakage and/or plug migration was noted in all trials, and either of these events resulted in pressure rises in the distal cavity. Most notably, differences of only 0.5 mm in the diameter of the canal resulted in marked changes in the occlusion and stability achieved. It is concluded that for the range of canal sizes anticipated intraoperatively, these synthetic plugs appear deficient to varying extents in their ability to occlude or remain stable in the intramedullary canal.

Potential disadvantages of post-operative adjuvant radiotherapy after anterior resection for rectal cancer: a pilot study of sphincter function, rectal capacity and clinical outcome

The aim of this study was to try to gauge the functional effect of post-operative adjuvant radiotherapy after potentially curative anterior resection for carcinoma of the rectum. Anorectal function was studied both in the laboratory and clinically in 59 patients, a median of 12 months (range 6-96) after operation. Nine patients received post-operative radiotherapy and 50 matched patients were treated by surgery alone. Though maximum resting anal pressures and maximum squeeze pressures were similar in the two groups of patients, the length and pressure profile of the anal sphincter were both markedly abnormal after radiotherapy. The capacity and compliance of the neorectum were diminished significantly after radiotherapy (maximum tolerated volume 53 ml vs 110 ml after surgery alone, P = 0.008, compliance 1.5 ml/cm H2O vs 3.7 ml/cm H2O after surgery alone, p = 0.018) and the amount of distension of the neorectum required to produced maximum inhibition of the anal sphincter during the rectoanal inhibitory reflex was also significantly diminished after radiotherapy (P = 0.005). Clinical anorectal function was worse among patients who had received radiotherapy, a greater proportion of whom experienced both urgency of defaecation and varying degrees of incontinence. Major faecal leakage necessitating the use of a pad was recorded in 3 of the 59 patients after radiotherapy (one of whom required a permanent colostomy), but in only 5 of 50 patients after surgery alone.

Evaluation of Angus, Charolais and Hereford as terminal sire breeds on Hereford and first-cross cows. II. Carcase characteristics and retail yield of progeny

The characteristics and retail yield of carcases of 482 Angus, Charolais and Hereford sired progeny out of straightbred Hereford (HxH), and first-cross Brahman x Hereford (BxH), Simmental x Hereford (SxH) and Friesian x Hereford (FxH) dams were evaluated. The cattle had been raised and slaughtered for either the vealer (both sexes), yearling domestic (both sexes) or the heavy export steer market. The data were analysed within market type, and at a constant age at slaughter (281, 478 and 829 days for vealer, yearling domestic and heavy export carcases respectively) and also at a constant hot P8 fat depth (4.6, 7.8 and 14.9 mm for the three markets respectively) and constant hot carcase weight (160, 200 and 343 kg for the three markets respectively). At a constant age, carcases of Charolais sired progeny were significantly (P < 0.05) heavier (8-16%, depending on market type), leaner, had larger eye muscle area and higher dressing percentage than those of Angus and Hereford sired progeny. This resulted in 12 to 17% (P < 0.05) more kg of boneless saleable meat (retail yield) from carcasses of Charolais sired progeny. At a constant hot P8 fat depth, the magnitude of the sire breed differences increased, whereas at a constant hot carcase weight, the differences became non-significant or were reduced in magnitude. At a constant age, progeny of BxH dams had higher ( P < 0.05) dressing percentage than those of the other dam breeds for all market types except the vealer market. Progeny of FxH dams had more (P < 0.05) channel and kidney fat than those of the other dam breeds, even at a constant hot P8 fat depth. Retail yield, as a percentage of the boned side, was highest for carcases of progeny of BxH dams and lowest for those of progeny of FxH dams (70.2% and 70.3% v. 69.1% and 69.2%, for vealer and yearling domestic carcases respectively, at a constant age). Sire and dam breed effects for the individual primal cuts, as percentages of the boned side, were not significant for most of the primal cuts, and where significant, the differences were very small.

Using paired-pulse facilitation to probe the mechanisms for long-term potentiation (LTP)

Paired-pulse facilitation (PPF) of excitatory synaptic transmission at Schaffer collateral synapses in the hippocampus was examined in relationship to long-term potentiation (LTP). PPF is a relatively simple-to-measure presynaptic form of synaptic plasticity. It is hypothesized that if the expression of LTP includes a presynaptic component, then PPF and LTP may interfere with one another. When averaged over more than 100 experiments, we observed no change in average PPF with LTP, as reported previously by a number of investigators. When individual experiments were analyzed, however, PPF significantly increased or decreased with LTP in direct relation to the initial value of PPF. There was also a linear relationship between the change in PPF and the magnitude of LTP. The PPF changes were specific to LTP and presynaptic in origin as they were input-specific and persisted with low concentrations of CNQX, GABAA and GABAB antagonists, different interstimulus intervals, and different Ca2+ concentrations. To understand the interaction between LTP and PPF, we constructed a simple model of LTP in which potential contributions by increases in three synaptic parameters were examined: the number of neurotransmitter release sites (n), the probability of release (p), and the postsynaptic unit potential (q). The data were fit by a model in which there were increases in n that changed the average p of the population, but not by a model that increased p or q alone. This is the first experimental evidence for an increase in the number of release sites with LTP, which could be due to pre- or postsynaptic mechanisms.

Decrease in the anorectal pressure gradient after low anterior resection of the rectum. A study using continuous ambulatory manometry

PURPOSE

Changes in anorectal function after low anterior resection of the rectum (LAR) often lead to symptoms of urgency and frequency of defecation, the anterior resection syndrome. It has been reported that preservation of part of the rectum improves clinical results, but why this should be remains unclear.

METHODS

We have carried out continuous ambulatory manometric studies in two groups of patients: 11 patients, a median of 11 (range, 5-96) months after LAR, in whom the median anastomotic level above the anal high-pressure zone was 0 (range, 0-2) cm; 9 patients, a median of 6 (range, 3-12) months after sigmoid colectomy, in whom the rectum remained in situ and who acted as controls.

RESULTS

Comparing the LAR group with controls, resting anal pressures were lower, median 68 (range 27-102) cm H2O vs. 95 (45-116) cm H2O (P < 0.05), and neorectal pressures were higher, 25 (0-48) cm H2O vs. 10 (0-10) cm H2O (P < 0.01). Thus the anorectal pressure gradients were less, 34 (0-74) cm H2O vs. 81 (35-113) cm H2O (P < 0.01). Slow-wave activity in the anal sphincter was present in six patients (55 percent) after coloanal anastomosis and eight patients (89 percent) after sigmoid colectomy. Sampling episodes were seen in only two patients (18 percent) after coloanal anastomosis and five patients (56 percent) after sigmoid colectomy. When clinical endpoints were compared (LAR vs. controls), bowel frequency in 24 hours was higher, 5 (3-8) vs. 2 (1-3) (P < 0.01); fecal leakage was more common, affecting seven patients (64 percent) vs. one patient (11 percent) (P < 0.05), and urgency of defecation was also more common.

CONCLUSIONS

The inferior clinical results observed after LAR compared with the results after sigmoid colectomy are thus in part because of higher neorectal pressure acting on a weakened sphincter mechanism. These observations lend support to the idea that neorectal capacity should be increased in patients who undergo low anterior resection.

Autonomously active protein kinase C in the maintenance phase of N-methyl-D-aspartate receptor-independent long term potentiation

In area CA1 of the hippocampus, the induction of long term potentiation (LTP) requires activation of either N-methyl-D-aspartate receptors (NMDA receptor-dependent LTP) or voltage-gated Ca2+ channels (NMDA receptor-independent LTP). We have investigated biochemical sequelae of NMDA receptor-independent LTP induction. We find that a persistent increase in second messenger-independent protein kinase C activity is associated with the maintenance phase of NMDA receptor-independent LTP. This increase in protein kinase C activity is prevented by blocking LTP with nifedipine, a Ca2+ channel antagonist, or kynurenic acid, a nonselective glutamate receptor antagonist. Additionally, we find an increase in the catalytic fragment of protein kinase C (PKM) in the maintenance phase of NMDA receptor-independent LTP, indicating that proteolytic activation of protein kinase C may account for its autonomous activation. This increase in the catalytic fragment of protein kinase C is also prevented by blocking LTP induction. These results are the first to demonstrate that persistent protein kinase C activation is a possible mechanism for the maintenance of NMDA receptor-independent LTP.

Coordinated activity of the new "rectum" and anal sphincter after sphincter-saving resection of the rectum for colitis or carcinoma

PURPOSE

The aim of this study was to determine whether coordinated activity exists across a stapled enteroanal anastomosis.

METHODS

Twenty-nine patients were studied for a median of one year after complete excision of the rectum and stapled enteroanal anastomosis; 12 patients underwent low anterior resection with coloanal anastomosis for carcinoma, and 17 patients underwent restorative proctocolectomy with ileoanal anastomosis.

RESULTS

Maximum anal resting pressures were slightly lower after coloanal anastomosis than after ileoanal anastomosis [median range, 56 (11-60) cm H2O, cf 69 (40-107) cm H2O, P = NS]. During distention of the neorectum, anal sphincter pressures at 2.5, 1.5, and 0.5 cm from the anal verge were significantly lower after coloanal anastomosis compared with after ileoanal anastomosis (P < 0.01 at each station). The volume of neorectal distention required to produce maximal inhibition of the anal sphincter was significantly less after coloanal anastomosis at 50 (range, 20-60) ml of air than after ileoanal anastomosis at 240 (range, 100-420) ml of air (P < 0.01). Minor fecal leakage and urgency of bowel action were significantly more common after coloanal anastomosis (P < 0.01).

CONCLUSION

Alterations in the dynamic response of the anal sphincter to distention of the neorectum may explain why the clinical results were better after ileal pouch-anal anastomosis than after coloanal anastomosis.

Goseki grading in gastric cancer: comparison with existing systems of grading and its reproducibility

A novel grading method which utilises intra-cellular mucin content and tubular differentiation (the Goseki grade) has been applied to 181 gastric cancers removed in potentially curative resections, and compared to conventional tumour grading (well, moderate, poor differentiation) and the Lauren, Ming and WHO classifications. The Goseki grade is significantly related to patient survival and, unlike the existing approaches, remains so after allowing for tumour stage in multivariate analyses. Potential relationships between the Goseki grade, direct tumour spread, lymph node involvement and survival have been investigated. Prognosis is particularly related to mucin content; 55% of patients with mucin-rich tumours dying within 5 years compared to 29% of those with mucin-poor cancers. A smaller proportion of mucin-poor cancers show lymph node involvement (N1 and N2) than mucin-rich tumours (52% v. 73%) and a smaller proportion of cancers showing good tubular differentiation exhibit widespread lymph node involvement (N2) than tubule-poor cancers (11% v. 28%). However, these differences did not achieve statistical significance. When compared to the existing classification or grading methods, the Goseki grade was found to be highly significantly correlated with the WHO and Lauren classifications and to conventional grading, but not to the Ming classification. These inter-relations are largely dependent upon tubular differentiation. There was no relationship between Goseki grade and the lymphocytic response around the tumour margin. Inter-observer agreement on the WHO type and the Lauren, Ming and Goseki grading methods was tested on 70 randomly selected cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of circumferential margin involvement in the local recurrence of rectal cancer

Local recurrence after resection for rectal cancer remains common despite growing acceptance that inadequate local excision may be implicated. In a prospective study of 190 patients with rectal cancer, we examined the circumferential margin of excision of resected specimens for tumour presence, to examine its frequency and its relation to subsequent local recurrence. Tumour involvement of the circumferential margin was seen in 25% (35/141) of specimens for which the surgeon thought the resection was potentially curative, and in 36% (69/190) of all cases. After a median 5 years' follow-up (range 3.0-7.7 years), the frequency of local recurrence after potentially curative resection was 25% (95% CI 18-33%). The frequency of local recurrence was significantly higher for patients who had had tumour involvement of the circumferential margin than for those without such involvement (78 [95% CI 62-94] vs 10 [4-16]%). By Cox's regression analysis tumour involvement of the circumferential margin independently influenced both local recurrence (hazard ratio = 12.2 [4.4-34.6]) and survival (3.2 [1.6-6.53]). These results show the importance of wide local excision during resection for rectal cancer, and the need for routine assessment of the circumferential margin to assess prognosis.

Changes in paired-pulse facilitation suggest presynaptic involvement in long-term potentiation

Long-term potentiation (LTP) is a use-dependent form of synaptic plasticity that is of great interest as a potential cellular substrate underlying memory. It is important to determine the pre- and/or postsynaptic locus of LTP expression in order to study its underlying mechanisms. Despite intensive investigation, however, its locus of expression remains uncertain. It has been hypothesized that if LTP expression includes a presynaptic locus then it may alter the expression of another presynaptically mediated form of potentiation like paired-pulse facilitation (PPF), which is an increase in a second population excitatory postsynaptic potential when it is elicited shortly after a first. Previous authors have found no change in PPF in association with LTP. We re-examined the hypothesis, however, to reconcile the negative PPF data with other data that have suggested presynaptic involvement in LTP. Extracellular recordings were made in area CA1 of the rat hippocampal slice preparation. Surprisingly, PPF both increased and decreased significantly in association with LTP. The changes in PPF occurred in a predictable way, however. They correlated inversely with initial PPF magnitude so that a larger initial PPF was associated with a decrease in PPF with LTP while a smaller initial PPF was associated with an increase. Because PPF increased or decreased in individual slices in association with LTP, the average PPF of all slices did not change, in agreement with previous studies. The changes in PPF were also specific to LTP; that is, they were input specific, were not due to changes in inhibition or nonspecific effects of high-frequency stimulation, were not due to active postsynaptic currents or their nonlinear summation, and PPF changed with the same time course as LTP. We conclude that the mechanism of early LTP expression includes at least the presynaptic locus. Two hypotheses regarding the presynaptic mechanism underlying LTP expression, which are consistent with finding both increases and decreases in PPF with LTP, are (1) that there is an increase in the number of release sites with LTP or (2) that there is an increase in both the number of release sites and the probability of neurotransmitter release. Increases in the probability of neurotransmitter release alone would not appear to account for our findings since such increases have been associated only with decreases in PPF. Our findings do not exclude additional postsynaptic involvement.(ABSTRACT TRUNCATED AT 400 WORDS)

Multiple components of calcium current in acutely dissociated dentate gyrus granule neurons

1. Specific Ca2+ channel blocker were used to isolate and characterize different components of whole cell Ba2+ current in granule neurons acutely dissociated from guinea pig hippocampal slices. 2. Granule cell Ba2+ current peaked around +5 mV, whether elicited by step or ramp commands, and was completely blocked by 100 microM Cd2+. 3. Saturating doses (> or = 5 microM) of the dihydropyridine antagonist, nimodipine, blocked 39% of the total current, and the inhibition was partially reversible. Nimodipine had a greater effect on current at the end of a depolarizing step, suggesting some voltage dependence of its action. 4. Saturating doses (> or = 3 microM) of omega-conotoxin-GVIA irreversibly blocked 21% of the total current and did not occlude subsequent nimodipine inhibition. 5. High concentrations (> or = 100 nM) of omega-agatoxin-IVA irreversibly blocked another 20% of the total current. The effect of omega-Aga-IVA was quite slow, but saturated after several minutes at 200 nM concentration. A high dose (1 microM) produced rapid effects that were used to quantify the magnitude of block. 6. When applied together, all three blockers inhibited nearly the same amount of total current (77%) as would be expected from the sum of each blocker applied individually (80%), suggesting that the three antagonists blocked different channel types. 7. Quantitatively similar results were obtained for the effect of each blocker alone and in combination on currents elicited by depolarizing ramp commands. Ramp currents blocked by each antagonist (difference ramps) all peaked near the same potential as the initial control ramp, indicating very similar activation properties for the three current components. Difference currents elicited by step commands similarly showed little difference among the three components in their kinetics of inactivation during relatively brief (30 ms) depolarizations. With longer steps, however, the omega-CgTX-GVIA-sensitive component showed some inactivation, whereas the omega-Aga-IVA-sensitive current did not inactivate. 8. The component of current resistant to all three blockers (approximately 23% of total current) was not inhibited by omega-conotoxin-MVIIC, but was half blocked by 50 microM Ni2+. This Ni(2+)-sensitive component showed relatively rapid inactivation and peaked at a somewhat lower potential (-10 mV) than the control current. The resistant current was also inactivated by approximately 50% by holding at -60 compared with -80 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

An audit of the treatment of cancer of the oesophagus

The treatment of cancer of the oesophagus in The General Infirmary at Leeds between the years 1975 and 1988 was reviewed. All cases with histologically proved cancer of the oesophagus were included, data being obtained from case notes, theatre operation books, endoscopy records, pathology records, and the Yorkshire Cancer Registry. Three hundred and sixteen patients were identified. Demographic details, mode of presentation, preoperative investigations, surgical management, methods of palliation, and survival data were entered into a database. The male to female ratio was 3:2 and the median age at presentation was 69 years (range 35-96). Surgical exploration was carried out in 134 of 316 patients (42%). Resection of the tumour, whether curative or palliative, was possible in 106 of 134 patients (79%). Operative (30 day) mortality was 27%. In 22 of 134 patients (16%), only intubation of the tumour was possible, while six patients (5%) had a thoracotomy or laparotomy alone. Median survival of the 106 patients after surgical resection was 292 days (range 0-14.2 years) and seven of them (7%) were still alive five years later. Of the remaining 182 patients (58%) who were not operated upon, 36 patients (11%) had a radical course of radiotherapy with a median survival of 175 days (range 80-453) and 146 patients (46%) either had endoscopic intubation (n = 64) or received no specific treatment (n = 82) with a median survival of 106 days (1-725) and 91 days (1-358) respectively. None of the 182 patients who did not have surgical treatment was alive at five years.

Distinctive features of immunoglobulin heavy chain variable region gene rearrangement in multiple myeloma

We have analysed the rearranged Ig heavy chain (IgH) genes in a series of 28 cases of multiple myeloma (MM), in order to extend the study of Ig heavy chain variable (VH) gene usage in B lymphoid malignancies and to explore the ontogenic compartment from which transformed precursor cells arise in this disease. We were able to amplify 28 rearranged alleles by polymerase chain reaction from 23 of these cases, using a common joining region (JH) amplimer together with a panel of VH family-specific amplimers. The pattern of VH family usage was similar to that reported in normal peripheral blood B cells with infrequent usage of VH5 and VH6 genes. However, nucleotide sequence analysis of 17 IgH alleles revealed rearrangement of other VH family members, closely related to known developmentally regulated VH genes, some of which are known to be associated with autoimmune specificities. In contrast to previous findings on more immature B lineage malignancies, the rearranged genes diverged extensively from consensus germline sequences, consistent with somatic mutation. These findings support the hypothesis that the major proliferating precursor in MM arises at, or following a stage of T cell-dependent germinal centre proliferation in lymphoid follicles.

Goseki histological grading of gastric cancer is an important predictor of outcome

TNM (tumour, node, metastases) staging has thus far been the most important guide to prognosis in patients with gastric cancer. Histological grading, in contrast, has not provided any additional information. Recently a novel grading system based on tubular differentiation and mucus production has been proposed, which was correlated with patterns of tumour spread found at necropsy. This study set out to assess its value as a determinant of survival after gastric resection. In a consecutive series of 211 patients who had potentially curative resection for gastric cancer, five histological grading systems were assessed: the Lauren type, the WHO type, degree of differentiation, the type of tumour border, and the lymphocytic response to the tumour and compared with the Goseki grading (I-IV). When T and N stage were taken into account, using Cox's proportional hazards model, only the Goseki grading added further to the ability to predict survival. The proportional hazards ratios were: node negative v node positive 6.5 T1 v T3 2.45; Goseki I v Goseki IV 3.1. Five year survival of patients with mucus rich (Goseki II and IV) T3 tumours was significantly worse than that of patients with mucus poor (Goseki I and III) T3 tumours (18% v 53%, p < 0.003). Goseki grading identifies subgroups of patients with a poorer prognosis than is predicted by TNM staging alone. It could prove useful in the selection of patients for adjuvant therapy after potentially curative resection for gastric cancer.

A comparison of public health care utilization by gay men and intravenous drug users with AIDS in San Francisco

A group of gay-identified men (n = 81) and intravenous drug users (n = 88) diagnosed with AIDS in San Francisco were surveyed regarding their use and satisfaction with their health care services. The interview contained a mix of qualitative and quantitative questions. The two groups of AIDS patients were not statistically different in terms of age or self-reported level of health during the previous 3 months, although the gay men had been diagnosed with AIDS somewhat longer (20 months) than the group of intravenous drug users (15 months). Analysis of the quantitative data revealed that intravenous drug users receive more medical care for HIV disease than did gay men and were equally satisfied with the care that they did receive. Analysis of the qualitative data showed that considerable agreement exists between the perceptions of both gay men and intravenous drug users of the health care system.

Dendritic attenuation of synaptic potentials and currents: the role of passive membrane properties

The dendritic trees of neurons are structurally and functionally complex integrative units receiving thousands of synaptic inputs that have excitatory and inhibitory, fast and slow, and electrical and biochemical effects. The pattern of activation of these synaptic inputs determines if the neuron will fire an action potential at any given point in time and how it will respond to similar inputs in the future. Two critical factors affect the integrative function of dendrites: the distribution of voltage-gated ion channels in the dendritic tree and the passive electrical properties, or 'electrotonic structure', upon which these active channels are superimposed. The authors review recent data from patch-clamp recordings that provide new estimates of the passive membrane properties of hippocampal neurons, and show, with examples, how these properties affect the shaping and attenuation of synaptic potentials as they propagate in the dendrites, as well as how they affect the measurement of current from synapses located in the dendrites. Voltage-gated channels might influence the measurement of 'passive' membrane properties and, reciprocally, passive membrane properties might affect the activation of voltage-gated channels in dendrites.

Digitized slice interposition in forensic dental radiographic identification. An in vitro study

Traditional methods of comparison involving the presence of missing teeth, dental restorations, and other pathological features may be difficult due to the reduction in dental restorations in today's population. This study demonstrates an alternative method of identification using digitized images. It utilizes anatomical structures such as dental root morphology and spatial relations of teeth roots and their supporting structures on simulated antemortem and postmortem radiographs as the basis for identification. A total of 39 mandibular specimens were used and two radiographs representing the antemortem and postmortem radiographs of each hemimandible were exposed by two operators using different x-ray generators. The radiographs were scanned and digitized. The identities of the antemortem and postmortem radiographs were kept from the operator. Following this, horizontal sections were digitally cut from the antemortem radiographs through the roots approximately halfway between the neck of the tooth and the root apex. This section was manipulated onto the postmortem radiograph by using a computer graphics program and a quantitative comparison of the alignment of normal dental anatomical landmarks was undertaken. The technique enabled perfect matching of all 39 specimens by antemortem and postmortem dental radiographs. The mean number of identifying points was 17.5 and the mean number of nonmatching points was 0.1. The mean concordance was 99.2% between the antemortem and postmortem radiographs.

A model for dendritic Ca2+ accumulation in hippocampal pyramidal neurons based on fluorescence imaging measurements

1. High-speed fluorescence imaging was used to measure intracellular Ca2+ concentration ([Ca2+]i) changes in hippocampal neurons injected with the Ca(2+)-sensitive indicator fura-2 during intrasomatic and synaptic stimulation. The results of these experiments were used to construct a biophysical model of [Ca2+]i dynamics in hippocampal neurons. 2. A compartmental model of a pyramidal neuron was constructed incorporating published passive membrane properties of these cells, three types of voltage-gated Ca2+ channels characterized from adult hippocampal neurons, voltage-gated Na+ and K+ currents, and mechanisms for Ca2+ buffering and extrusion. 3. In hippocampal pyramidal neurons imaging of Na+ entry during electrical activity suggests that Na+ channels, at least in sufficient density to sustain action potentials, are localized in the soma and the proximal part of the apical dendritic tree. The model, which incorporates this distribution, demonstrates that action potentials attenuate steeply in passive distal dendritic compartments or distal dendritic compartments containing Ca2+ and K+ channels. This attenuation was affected by intracellular resistivity but not membrane resistivity. 4. Consistent with fluorescence imaging experiments, a non-uniform distribution of Ca2+ accumulation was generated by Ca2+ entry through voltage-gated Ca2+ channels opened by decrementally propagating Na+ action potentials. Consequently, the largest increases in [C2+]i were produced in the proximal dendrites. Distal voltage-gated Ca2+ currents were activated by broad, almost isopotential action potentials produced by reducing the overall density of K+ channels. 5. Simulations of subthreshold synaptic stimulation produced dendritic Ca2+ entry by the activation of voltage-gated Ca2+ channels. In the model these Ca2+ signals were localized near the site of synaptic input because of the attenuation of synaptic potentials with distance from the site of origin and the steep voltage-dependence of Ca2+ channel activation. 6. These simulations support the hypotheses generated from experimental evidence regarding the differential distribution of voltage-gated Ca2+ and Na+ channels in hippocampal neurons and the resulting voltage-gated Ca2+ accumulation from action and synaptic potentials.

Stricture at the pouch-anal anastomosis after restorative proctocolectomy

PURPOSE

The aim of this study was to determine what factors may be responsible for the development of a stricture at the pouch-anal anastomosis after restorative proctocolectomy.

METHODS

A consecutive series of 115 patients was studied retrospectively a median of 34 months (range, 4-100 months) after operation or ileostomy closure. The procedure failed in 11 patients (9.6 percent) who subsequently had to have a permanent ileostomy. Another two patients were excluded from the analysis, one of whom was awaiting ileostomy closure, whereas the other had a stricture due to a desmoid tumor. Of the remaining 102 patients, 39 (38 percent) developed an ileoanal anastomotic stricture, which was severe and persistent in 16 percent.

RESULTS

The results were analyzed with the aid of multivariate logistic regression analysis. Factors which predisposed significantly to the development of an ileoanal anastomotic stricture were 1) use of the 25-mm (small) diameter stapling gun (P = 0.05), 3) use of a defunctioning ileostomy (P = 0.03), and 4) anastomotic dehiscence and pelvic sepsis (P = 0.03). The single patient whose operation failed because of a stricture had also developed pelvic sepsis associated with an anastomotic dehiscence.

CONCLUSIONS

The eventual clinical, functional outcome after dilation of a stricture in the 39 patients who developed a stricture was as good as the outcome in the 63 patients who did not a develop stricture.

Secretory and absorptive activity of oesophageal epithelium: evidence of circulating mucosubstances

The space between the oesophageal basal and prickle epithelial cells appears empty by standard ultrastructural preparative techniques. Fixation of human oesophageal biopsies with a variety of agents, including tannic acid, glutaraldehyde-lysine, cetylpyridinium chloride and Ruthenium Red shows that this space is filled with mucosubstances, some free, some attached to the cells as a glycocalyx. There is evidence that this material is secreted constitutively by the basal and prickle cells. This secretion may be changed or blocked by incubating oesophageal biopsies in the presence of colchicine or dinitrophenol. Incubation at 16 degrees C has the same effect. Absorption from the intercellular space may be followed using the fluid phase marker, horseradish peroxidase. Early endosomes may also be shown by their acid phosphatase activity. Incubation of biopsies at 20-22 degrees C allows early endosomes to accumulate material, but not pass it on the late endosomes.