Site-specific N-terminal auto-degradation of human serum albumin

Human serum albumin prepared by blood fractionation for clinical purposes was found to degrade when stored at or above 30 degree C. Mass spectrometry and N-terminal sequencing of the protein identified degradation corresponding to the loss of the first two residues, aspartic acid and alanine. The reaction was shown to be dependent upon temperature and the N-terminal alpha-amino group. In addition, comparison with serum albumins derived from other species showed that the instability of the N-terminus was specific to the human albumin sequence. An intact aspartyl-alanyl dipeptide, purified from degraded albumin solutions, differed substantially from a synthetic dipeptide on amino acid analysis, N-terminal sequencing and NMR. It is suggested that the released dipeptide may be cyclic, implying a novel cleavage mechanism.

A new structural transition of serum albumin dependent on the state of Cys34. Detection by 1H-NMR spectroscopy

1. Reactions of fatty-acid-free bovine serum albumin and recombinant human albumin with a range of antiarthritic gold(I) complexes [auranofin, deacetylated auranofin, triethylphosphinegold(I) chloride] and related thiols (thioglucose, tetraacetylthioglucose, glutathione, dithiothreitol) have been investigated using 1H-NMR spectroscopy. 2. In reactions of albumin with auranofin, tetraacetylthioglucose and dithiothreitol, release of cystine was detected, whereas for deacetylated auranofin, thioglucose and glutathione, mixed disulphides with cysteine were produced. It has been previously proposed that Cys34 of human and bovine serum albumins is partly blocked by disulphide formation with cysteine and glutathione. The above reactions lead to deblocking by thiol-disulphide interchange reactions. No release of glutathione from albumin was detected. 3. Changes in the His H epsilon 1 regions of the 1H-NMR spectra show that albumin exists in two structural forms dependent on whether the side-chain of Cys34 is a free thiolate, or blocked by gold(I)triethylphosphine, by disulphide formation with cysteine or by another form of oxidation. We propose that Cys34 is either in a buried or in an exposed environment; the possible molecular basis of the structural change is discussed. 4. The relationship between reactions at Cys34, cysteine release, and the observed structural transition are discussed in terms of chrysotherapy, albumin metabolism and the use of gold(I) as a heavy atom derivative in X-ray crystallographic studies of albumins.

Adenosinergic modulation of CA1 neuronal tolerance to glucose deprivation in organotypic hippocampal cultures

Glucose deprivation produced neuronal degeneration of CA1 pyramidal neurons in hippocampal slice cultures. The effects of the adenosine agonist cyclohexyladenosine (CHA) and antagonist cyclopentylxanthine (CPX) on CA1 neuronal loss following hypoglycemia was examined using propidium iodide fluorescence as an indicator of cell death. The intensity of propidium iodide fluorescence in hippocampal area CA1 was quantified using Optimas image analysis software. Following 2 or 3 h of glucose deprivation, CPX significantly enhanced injury in the CA1 region while CHA provided significant protection. These results suggest that adenosine plays an important role in endogenous neuronal protection during hypoglycemic injury, and also supports a role for the use of adenosine agonists as neuroprotective agents.

Calcitonin gene-related peptide modulates pulmonary vascular reactivity in isolated rat lungs

The role of calcitonin gene-related peptide (CGRP) in modulating hypoxic pulmonary vasoconstriction was assessed. The effects of CGRP and its antagonist [CGRP-(8-37)] on responses to acute hypoxia (3% O2) and angiotensin II (ANG II; 0.4 microgram) were studied in isolated lungs of male Sprague-Dawley rats perfused with a salt solution. Rats with pulmonary hypertension, induced by simulated altitude exposure, were also used to determine the actions of CGRP in a remodeled pulmonary vascular bed. In normotensive (NT) and altitude-exposed (AE) lungs, CGRP injections (10 nM), given after stable pressor responses were attained, attenuated (P < 0.05) subsequent hypoxic pressor responses. Pretreatment with CGRP-(8-37) (10 nM) enhanced (P < or = 0.05) initial ANG II-induced pressor responses in both AE and NT lungs. CGRP-(8-37) pretreatment (10 nM) had little influence on the hypoxic pressor responses in either NT or AE lungs. Results indicate that CGRP modulates hypoxic pulmonary vasoconstriction and that CGRP-(8-37) enhances pressor responses to ANG II in NT and AE rat lungs.

Residual lung volume and ventilatory muscle strength changes following maximal and submaximal exercise

In order to evaluate a mechanism which may be responsible for the often observed acute increase in residual lung volume (RV) following exercise, 12 non-smoking males (20-30 yrs) performed two bouts of exercise on separate days; one to maximal heart rate (HRmax) and one to 85% of HRmax for 20 min. Prior to exercise and at 5, 15, 30, 60 and 120 min post-exercise, the following parameters were measured: RV, forced vital capacity (FVC), forced expiratory volume (FEV1.0), forced expiratory flow (FEF75-85), maximal expiratory pressure (PEmax), and maximal inspiratory pressure (PImax). Significant (p < 0.05) increases occurred in RV at 5, 15 and 30 min following maximal exercise and at 5 and 30 min after submaximal exercise. Changes in RV between the two exercise bouts were generally greater (p < 0.05) for maximal exercise. Accompanying the increases in RV were significant (p < 0.05) decreases in PEmax and decreases in FVC, while FEV1.0 and FEF75-85 remained generally unchanged or were slightly elevated. The data suggest that decreases in expiratory muscle strength due to fatigue may in part be responsible for increases in RV.

pH-induced structural changes in human serum apotransferrin. pKa values of histidine residues and N-terminal amino group determined by 1H-NMR spectroscopy

The binding of apotransferrin (80 kDa) to the transferrin receptor is known to be highly pH-dependent. We have investigated pH-induced structural changes in human serum apotransferrin over the pH* (meter reading in D2O solutions) range 2.5-11 using 1H-NMR spectroscopy. The pKa values of 14 (possibly 15) of the 19 His residues in the protein have been determined as well as that of the terminal amino group (Val1, 7.75). About eight His residues deprotonate when the pH* is raised from the endosomal value of about 5.5 to the blood plasma value (7.4). Four His residues have pKa < 6. Sharp discontinuities in the His titration curves were observed below pH 4.3 and at pH 3.5 molten globule states were detected.

Involvement of a lysine residue in the N-terminal Ni2+ and Cu2+ binding site of serum albumins. Comparison with Co2+, Cd2+ and Al3+

We report one-dimensional and two-dimensional 1H-NMR studies of the binding of Ni2+, Cu2+, Co2+, Cd2+ and Al3+ to defatted bovine and human serum albumins. The diamagnetic shifts induced by Ni2+, and paramagnetic effects due to Cu2+, were consistent with strong binding to a square-planar site formed by the three N-terminal amino acid residues (Asp-Thr-His for bovine, and Asp-Ala-His for human albumin). In contrast to previous studies on isolated 1-24 N-terminal peptide, a Lys residue also appeared to be involved in the binding site, and is assigned as Lys4. A second His residue is also close to the Cu2+/Ni2+ binding site in bovine serum albumin and is assigned to His59 (not present in human albumin). Co2+ caused specific perturbation of the resonances for the three N-terminal residues as well as those for Lys4. This is the first evidence for Co2+ binding to the N-terminal metal site of serum albumin. Neither Al3+ nor Cd2+ perturbed resonances for the N-terminal amino acids, but bind elsewhere in the protein.

Influence of carbon dioxide on venous gas emboli production during altitude decompression in goats

Goats (N = 7) were decompressed from 1,500 m to 9,150, 9,750, or 10,400 m simulated altitude while breathing CO2 tensions of 0, 15, 30, or 46 mm Hg in O2 during 15-min prebreathing and 30-min peak altitude exposures. Risk of decompression sickness was determined by detecting venous gas emboli (VGE) in the pulmonary artery with an implanted Doppler cuff. VGE scores were calculated using the ratio of cardiac cycles containing VGE to total cardiac cycles. The VGE scoring methodology proved sensitive to standard treatment effects (air versus O2 prebreathing). No significant change in VGE scores as a result of varying the inspired CO2 level was detected. Further, no significant change in cardiac index occurred during the various CO2 exposures, and VGE scores were not correlated with cardiac index. Ground-level studies revealed the tension of end-tidal CO2 was significantly elevated at all three levels of inspired CO2, but no change in cardiac index was observed. Short-duration breathing of CO2 in oxygen failed to significantly reduce the risk of decompression sickness as assessed by VGE production.

Pulmonary vascular responsiveness in rats following neonatal exposure to high altitude or carbon monoxide

Exposure of adult and neonatal rats to high altitude increases pulmonary vascular responsiveness during the exposure. A study was undertaken to determine if a short exposure of neonatal rats to either high-altitude or carbon monoxide (CO) hypoxia would cause persistent alterations in pulmonary vascular responsiveness postexposure. One-day-old male Sprague-Dawley rats were obtained as 16 litters of 10-12 pups each. At 2 days of age, 4 litters were exposed to CO (500 ppm) for 32 days, and 4 litters were exposed to ambient air (AIR) in Detroit (200 m). Another 4 litters were exposed to 3500 m altitude (ALT) in a chamber for 32 days, and 3 litters were exposed to ambient conditions in Fort Collins (CON, 1524 m). After the exposures, all rats were maintained at 1524 m. At 2, 40, 76, and 112 days postexposure, lungs were isolated and perfused with Earle's salt solution (+Ficoll, 4 g%). Pulmonary vascular responsiveness was assessed by dose responses to angiotensin II (AII, 0.025-0.40 micrograms) and acute hypoxia (3% O2 for 3 min). AII responses were higher in ALT vs CON rats at all ages, but no differences were noted between CO and AIR rats. Acute hypoxic responses were higher in ALT versus CON rats at 2 and 40 days postexposure, but no differences were noted between CO and AIR rats. Baseline pulmonary vascular resistance and pulmonary arterial pressure (in isolated lungs) were higher in ALT rats at all four ages compared to the other three groups. Both the ALT and CO rats displayed hypertrophy of the right ventricle (RV) and the left ventricle (LV) at the termination of treatment and elevated hematocrit. LV hypertrophy and polycythemia regressed with time, but RV hypertrophy remained significant in the ALT rats through 112 days postexposure. The results indicate that neonatal exposure to ALT, but not CO, causes a persistent increase in pulmonary vascular responsiveness and RV hypertrophy for at least 112 days after termination of the exposure.

Local failure and margin status in early-stage breast carcinoma treated with conservation surgery and radiation therapy

OBJECTIVE

The authors determined whether microscopically positive surgical margins are detrimental to the outcome of early stage breast cancer patients treated with conservation surgery and radiation therapy.

SUMMARY BACKGROUND DATA

The optimal extent of breast surgery required for patients treated with conservation surgery and radiation therapy has not been established. To achieve breast preservation with good cosmesis, it is desirable to resect as little normal tissue as possible. However, it is critical that the resection does not leave behind a tumor burden that cannot be adequately managed by moderate doses of radiation. It is not known whether microscopically positive surgical margins are detrimental to patient outcome.

METHODS

The records of 259 consecutive women (262 breasts) treated with local excision (complete removal of gross tumor with a margin) and axillary dissection followed by radiation therapy for clinical stage I and II infiltrating ductal breast cancer at Duke University Medical Center and the University of North Carolina between 1983 and 1988 were reviewed. Surgical margins were considered positive if tumor extended to the inked margins; otherwise the margins were considered negative. Margins that could not be determined, either because the original pathology report did not comment on margins, or because the original specimen had not been inked were called indeterminate.

RESULTS

Of the 262 tumors, 32 (12%) had positive margins, 132 (50%) had negative margins, and the remaining 98 (38%) had indeterminate margins. There were 11 (4%) local failures; 3/32 (9%) from the positive margin group, 2/132 (1.5%) from the negative margin group, and 6/98 (6%) from the indeterminate group. The actuarial local failure rates at 5 years were 10%, 2%, and 10%, respectively, p = 0.014 positive vs. negative, p = 0.08 positive vs. indeterminate (log rank test). Margin status had no impact on survival or freedom from distant metastasis; 63 patients who originally had positive or indeterminate margins were re-excised. Two of 7 with positive margins after re-excision versus 1/56 rendered margin negative had a local recurrence.

CONCLUSIONS

The authors recommend re-excision for patients with positive margins because of improved local control of those rendered margin negative and identification of those patients at high risk for local failure (those who remain positive after re-excision). Because margin status impacts on local control, tumor margins after conservation surgery should be accurately determined in all patients.

Pulmonary and systemic vascular responsiveness to TNF-alpha in conscious rats

Endotoxin decreases pulmonary vascular reactivity. Because tumor necrosis factor-alpha (TNF-alpha) is a primary mediator of endotoxemia, we tested whether TNF-alpha altered pulmonary vascular reactivity in conscious adult female rats. Osmotic pumps were implanted intraperitoneally, and low-dose TNF-alpha (62 micrograms, TNF62; n = 7), high-dose TNF-alpha (> or = 250 micrograms, TNF250; n = 5), or saline (n = 5) was administered for 2 wk. Pulmonary pressor responses to 14% O2 and angiotensin II (ANG II, 0.0206 micrograms/min for 10 min) were measured without (day 13) or after (day 14) administration of nitro-L-arginine (4.4 mg/kg iv), an inhibitor of endothelium-derived relaxing factor (EDRF). TNF-alpha administration slightly decreased (P < or = 0.08) baseline pulmonary arterial pressure in TNF250 rats and decreased (P < or = 0.05) hypoxia- and ANG II-induced constrictions in TNF62 and TNF250 rats. Whereas nitro-L-arginine potentiated (P < or = 0.05) pressure responses in control rats, it had no effect on hypoxic responses in TNF-alpha-treated rats. Nitro-L-arginine increased (P < or = 0.05) ANG II-induced vasoconstriction in TNF-alpha-treated rats, but the pulmonary arterial pressure response was still lower (P < or = 0.05) in TNF250 than in control and TNF62 rats. These results suggest that chronic TNF-alpha decreases 1) pulmonary vascular reactivity in the intact rat, 2) hypoxic pulmonary vasoconstriction by a mechanism that is independent of EDRF, and 3) ANG II-induced constriction by a mechanism that is partly EDRF dependent.

pH-induced structural transitions of bovine serum albumin. Histidine pKa values and unfolding of the N-terminus during the N to F transition

1. Titration curves have been constructed for all the resolvable resonances of defatted bovine serum albumin [pH meter readings in 2H2O solution (pH*) 2-10], including complete curves for six His residues and partial curves for a further four. Three His residues have unusually low pKa values (less than 5.5). 2. Abrupt discontinuities in the titration curves of nearly all resonances were observed near pH 4.3 (N to F transition), together with a marked loss of chemical shift dispersion at low pH*. No such loss of dispersion occurs in the high pH region previously associated with the N to B transition (approximately pH 8). The NMR data provide strong evidence that the N to F transition is not localised in domain III as had been previously suggested. 3. A localised unfolding of the N-terminal region occurs below pH* 4.5.

Detection of aluminium(III) binding to citrate in human blood plasma by proton nuclear magnetic resonance spectroscopy

Reactions of Al3+ (50-500 mumol l-1) with intact blood plasma and its low relative molecular mass ultrafiltrate (< 5 kDa) have been studied by proton nuclear magnetic resonance spectroscopy. Binding to citrate was detected and was reversed by addition of desferrioxamine. The use of combined exponential and sine-bell functions for the resolution enhancement of spectra of plasma is illustrated.

Muscular strength capacity and altitude response

To determine the relationship between muscular strength and altitude response, two groups of 7 and 8 subjects were selected from 40 healthy male volunteers, as either high-strength (HS) or low-strength (LS) by performance on a battery of strength tests. There was no difference in hypoxic ventilatory response (HVR) between groups at normobaria. The 4 h hypobaric conditions in a Hypo-hyperbaric Chamber (PBar = 429) produced qualitatively similar altitude-induced physiological responses. However, the LS group showed a lower SaO2 at 2 and 4 h of hypoxia (p < 0.05). Furthermore, PETCO2 and PVCO2 were lower and PETO2, PVO2, and pH were greater in the HS group during hypobaria, although these differences did not achieve statistical significance. Muscular strength index (body weight divided by strength test values) was negatively correlated with PvCO2 (r = -0.63, p = 0.0074), PETCO2 (r = -0.62, p = 0.006) and positively with SaO2 (r = 0.54, p = 0.018) at altitude. These findings suggest that the HS group may have become more hypocapnic and alkalotic (suggesting a greater ventilatory response), and consequently less hypoxic than the LS group.

Heart and lung alterations in neonatal rats exposed to CO or high altitude

We wished to determine whether cardiac changes produced by CO are related to the development of pulmonary hypertension and whether they are specific for CO or also occur with high-altitude exposure. Newborn male Sprague-Dawley rats were exposed to 500 ppm CO for 32 days (CO) at Detroit, MI or to 11,500-ft simulated altitude at Fort Collins, CO (barometric pressure 495 Torr; 11K); ambient air controls were maintained at Detroit (657 ft, 200 m; AIR) and at Fort Collins (5,000 ft, 1,524 m; 5K). Rats were maintained at Fort Collins after 34 days of age. Hematocrit was elevated to a greater extent in the CO than in the 11K group 2 days postexposure; however, no differences existed 40, 76, or 112 days postexposure. Right ventricle (RV) and left ventricle plus septum (LV + S) mass in CO rats were increased 38.0 and 37.4%, respectively, relative to the AIR group 2 days after CO exposure; RV and LV + S in the 11K group were increased 55.7 and 9.3%, respectively, relative to the 5K group. Cardiac hypertrophy declined in the CO and 11K groups postexposure but remained significant for the RV, reaching 20.7% above the AIR group (CO) and 29.7% above the 5K group (11K) at 145 days of age. By use of an in vitro preparation, pulmonary vascular resistance (PVR) and pulmonary arterial pressure were significantly increased immediately after altitude but not after CO exposure and remained elevated in adulthood after altitude exposure. PVR was correlated with hematocrit in altitude- but not in CO-exposed rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake of Al3+ into the N-lobe of human serum transferrin

We have studied the binding of Al3+ to human serum apotransferrin (80 kDa) and recombinant N-lobe human apotransferrin (40 kDa) in 0.1 M-sodium bicarbonate solution at a pH meter reading in 2H2O (pH*) of 8.8 using 1H n.m.r. spectroscopy. The results show that for the intact protein, preferential binding of Al3+ to the N-lobe occurs. Molecular modelling combined with an analysis of ring-current-induced shifts suggest that n.m.r. spectroscopy can be used to probe hinge bending processes which accompany metal uptake in solution.

Acute and long-term TNF-alpha administration increases pulmonary vascular reactivity in isolated rat lungs

Tumor necrosis factor-alpha (TNF-alpha) causes pulmonary hypertension and arterial hypoxemia, but the mechanisms are unknown. We conducted two experiments to test the hypothesis that TNF-alpha alters pulmonary vascular reactivity, which in turn could cause either pulmonary hypertension or arterial hypoxemia. In experiment 1, rats were given acute or long-term injections of TNF-alpha (recombinant human) in vivo. Rats treated acutely received either saline or TNF-alpha (40 micrograms/kg iv in saline) 3 min (TNF-3 min; n = 8), 20 min (TNF-20 min; n = 8), or 24 h (TNF-24 h; n = 5) before the lungs were isolated. Rats treated chronically received injections of either saline or TNF-alpha (250 micrograms/kg ip in saline) two times per day for 7 days (TNF-7 days; n = 9). Lungs were isolated and perfused with Earle's salt solution (+2 g/l NaHCO3 + 4 g/100 ml Ficoll), and vascular reactivity was tested with acute hypoxia (3 min; 3% O2) and angiotensin II (ANG II; 0.025-0.40 micrograms). Pulmonary pressor responses to hypoxia were greater (P less than 0.05) in TNF-20 min and TNF-7 day groups. ANG II responses were increased (P less than 0.05) in TNF-7 day rats. In experiment 2, lungs were isolated and perfused and received direct pulmonary arterial injections of TNF-alpha (0.2, 2.0, and 20 micrograms) or saline, after stable responses to hypoxia and ANG II (0.10 microgram) were attained. Reactivity was not different between control and TNF-alpha rats before the injections, but TNF-alpha increased (P less than 0.05) responses to hypoxia and ANG II.(ABSTRACT TRUNCATED AT 250 WORDS)

Is transcutaneous electrical nerve stimulation of any value during cervical laser treatment?

OBJECTIVE

To assess the value of transcutaneous electrical nerve stimulation (TENS) during cervical laser therapy.

DESIGN

Randomized three arm controlled clinical trial comparing (i) TENS, (ii) local anaesthetic and (iii) TENS plus local anaesthetic (direct infiltration of 2% lignocaine and 0.03 iu/ml octopressin).

SETTING

Colposcopy Unit adapted to run randomized trials.

SUBJECTS

100 women with CIN and no previous experience of cervical surgery.

MAIN OUTCOME MEASURE

Visual linear analogue pain scores.

RESULTS

The median pain score associated with TENS was greater than the score associated with local anaesthesia (23% compared with 17%; P = 0.1). Combining TENS with local anaesthesia did not further reduce pain scores.

CONCLUSION

Although there was considerable consumer satisfaction with TENS it provided no additional pain relieving effect in addition to direct infiltration of lignocaine and it is inferior to lignocaine alone. We are unable to advocate the use of TENS for laser treatment of the cervix.

Proton NMR studies of bovine serum albumin. Assignment of spin systems

A variety of one- and two-dimensional 1H-NMR methods have been applied to the study of defatted 66.5-kDa bovine serum albumin in solution. 1. The majority of the protons gave rise to broad unresolved resonances and spectral enhancement methods for one-dimensional spectra were investigated in detail. A combination of exponential and sine-bell functions was particularly effective. 2. The presence of contaminating glycoproteins in some commercial samples of bovine serum albumin was readily detectable from their N-acetyl resonances at about 2.1 ppm. 3. The release of bound Cys (from mixed disulphide at Cys34) was observed after addition of dithiothreitol. 4. Through the use of two-dimensional shift-correlated spectroscopy, assignments of some 80 spin systems to amino acid type were made. 5. The pKa of the N-terminal Asp was measured as 7.8 (0.1 M phosphate buffer, 310 K). 6. 1H NMR spectra of bovine, human, porcine and rat serum albumins have been compared. Using sequence comparisons, specific assignments have been made for the N-terminal residues of bovine (Asp-Thr-His), human (Asp-Ala-His), porcine (Asp-Thr-Tyr) and rat (Glu-Ala-His) albumins, and for Thr189, Tyr155 and His59/377 of bovine albumin. 7. These NMR data suggest that certain local regions of bovine serum albumin are highly mobile yet structured in solution, and demonstrate that the application of both one- and and two-dimensional NMR methods will allow more detailed investigations of structural transitions in serum albumins induced by, for example, pH, drug and metal binding.

Factors influencing the idiopathic development of pulmonary hypertension in the fawn hooded rat

Fawn hooded rats (FHR), a strain of rat with a hereditary bleeding tendency due to a genetic defect in platelet aggregation, have recently been found to develop pulmonary hypertension. However, whether the pulmonary hypertension in FHR has a genetic basis or simply reflects the influence of extrinsic factors known to increase pulmonary artery pressure in other rat strains has not been fully evaluated. To further examine the structural and hemodynamic changes of pulmonary hypertension in FHR, and to investigate the extent to which alveolar hypoxia may have promoted these abnormalities, hemodynamic and morphometric measurements were made in FHR (4 to 24 wk) and compared with age-matched Sprague-Dawley (SDR) control rats. Increases in mean pulmonary artery pressure, total pulmonary resistance, and right ventricular enlargement were present in both male and female FHR and were evident at an early age (4 wk). Morphometric analysis of barium gelatin-infused lungs revealed marked pulmonary vascular remodelling in FHR characterized as extension of muscle into more peripheral pulmonary vessels, medial hypertrophy of proximal vessels, and reduced number of barium-filled arteries. The increases in pulmonary artery pressure in FHR were not due to the influence of more severe hypoxia, hypoventilation, or polycythemia, as blood gas tension and hematocrit were similar in FHR and SDR. Moreover, we found that pulmonary hypertension could be transmitted to backcross and second filial generation offspring arising from selective matings between FHR and control Wistar Kyoto rats, confirming the heritable basis for pulmonary hypertension in the FHR.