Antihypertensive efficacy and safety of losartan alone and in combination with hydrochlorothiazide in adult African Americans with mild to moderate hypertension

BACKGROUND

African Americans with hypertension, particularly those with more severe blood pressure elevations, are generally less responsive to monotherapy from any antihypertensive class. These patients usually require treatment with drugs from > or = 2 antihypertensive classes to achieve adequate blood pressure control.

OBJECTIVE

The purpose of this study was to assess the antihypertensive efficacy and safety of losartan alone and in combination with hydrochlorothiazide (HCTZ) in African American adults with mild to moderate hypertension.

METHODS

In this 12-week, multicenter, double-blind, randomized, parallel-group, placebo-controlled study, African American patients were randomized in a 3:3:1 ratio to I of 3 treatment groups: placebo, losartan monotherapy (50 to 150 mg), or losartan plus HCTZ (50/0 to 50/12.5 to 100/25 mg). Doses were titrated at weeks 4 and 8 if sitting diastolic blood pressure (SiDBP) was > or = 90 mm Hg. Safety was assessed by determining the incidence of clinical and laboratory Adverse events and evaluating mean changes in pulse, body weight, electrocardiographic parameters, and laboratory test results.

RESULTS

A total of 440 patients were randomized-188 to placebo, 193 to losartan monotherapy, and 59 to losartan/HCTZ; 391 completed the study. At week 12, the response rate with losartan monotherapy was 45.8%, with a significant (P < or = 0.01) lowering in mean SiDBP by 6.6 mm Hg compared with placebo; the response rate with placebo was 27.2%, with a mean SiDBP reduction of 3.9 mm Hg. Sitting systolic blood pressure (SiSBP) was significantly lowered with losartan monotherapy, by 6.4 mm Hg, compared with placebo (reduction of 2.3 mm Hg). The response rate with losartan/ HCTZ was 62.7%, with reductions in SiSBP and SiDBP of 16.8 mm Hg and 10.8 mm Hg, respectively (P < or = 0.01 vs placebo and losartan monotherapy). The incidence of clinical adverse events was comparable in the 3 treatment groups.

CONCLUSIONS

The results of this study suggest that in African American patients, losartan monotherapy was significantly more effective than placebo in lowering SiSBP and SiDBP. Moreover, the losartan/ HCTZ combination regimen resulted in significant and clinically meaningful additional reductions in SiSBP and SiDBP compared with losartan monotherapy or placebo. Losartan monotherapy and the losartan/HCTZ regimens were generally as well tolerated as placebo.

Comparison of amlodipine or nifedipine treatment with developing congestive heart failure: effects on myocyte contractility

BACKGROUND

Past studies have suggested that amlodipine, a dihydropyridine L-type Ca(2+) channel antagonist, may exert useful effects in congestive heart failure (CHF). The present study examined the effects of amlodipine or nifedipine treatment in a model of developing CHF on left ventricular (LV) pump function and myocyte contractility.

METHODS AND RESULTS

Pigs (25 kg) were randomly assigned to 1 of 4 groups: 1) pacing-induced CHF (rapid atrial pacing at 240 bpm) for 3 weeks (n = 9), 2) concomitant Ca(2+) channel blockade with amlodipine (1.5 mg/kg/day) and rapid pacing (n = 7), 3) concomitant Ca(2+) channel blockade with nifedipine (0.7 mg/kg twice daily) and rapid pacing (n = 7), and 4) sham controls (n = 7). LV fractional shortening fell with pacing CHF from baseline values (17% +/- 1% v 42% +/- 1%, P <.05). With rapid pacing and concomitant amlodipine treatment, LV fractional shortening increased from pacing CHF values (24% +/- 1%, P <.05) but was unchanged with concomitant nifedipine treatment (20% +/- 2%, P =.2). LV myocyte velocity of shortening, as measured by high speed videomicroscopy, was reduced with pacing CHF compared with controls (42 +/- 2 microm/s v 87 +/- 9 microm/s, P <.05), and increased from pacing CHF values with amlodipine or nifedipine treatment (62 +/- 8 microm/s, 64 +/- 4 microm/s, respectively; P <.05). Inotropic response to extracellular Ca(2+) (8 mmol/L) was reduced with pacing CHF (94 +/- 5 microm/s v 160 +/- 15 microm/s, P <.05) and increased from CHF values with amlodipine or nifedipine treatment (132 +/- 14 microm/s and 133 +/- 7 microm/s, respectively, P <.05) CONCLUSIONS: These results suggest that the primary mechanism for the effects of amlodipine on myocyte contractility in developing CHF is because of direct Ca(2+) channel blockade.

Maintenance venom immunotherapy administered at 3-month intervals is both safe and efficacious

BACKGROUND

Maintenance venom immunotherapy (MVIT) is usually administered to patients with venom allergy at 4- to 6-week intervals for at least 3 to 5 years. The small number of studies assessing the possibility of extending the maintenance interval (MI) included either too small a population and patients with only vespid and not bee venom (BV) allergy or relied on reaction to field stings only.

OBJECTIVE

We sought to assess the safety and efficacy of MVIT given at 3-month intervals to a large population of patients allergic to both yellow jacket venom and BV.

METHODS

In all patients undergoing venom immunotherapy, MI was gradually extended to 3 months. Systemic reactions (SRs) to immunotherapy injections or to field stings were regularly recorded. Some of the patients were also deliberately sting challenged during the 3-month interval. Patients discontinuing MVIT were interviewed regarding their responses to field re-stings, and in some of them, an in-hospital sting challenge was performed.

RESULTS

One hundred sixty patients mostly allergic to BV were enrolled in the study. Failure to reach the 3-month interval was observed in 6 (3.8%) patients, originating in failure to reach the full maintenance dose in most of them. SRs to MVIT administered at 3-month intervals were observed in 2.6% of the patients. One of 36 patients who experienced a field sting during the 3-month interval had an objective mild SR (2.8%). Two (4.5%) of 44 patients who were deliberately stung during the 3-month interval had mild SRs. After discontinuation of MVIT, 2 (8.3%) of 24 patients who experienced a field sting had an SR. Both were allergic to yellow jacket venom. Three to 82 months after discontinuation of MVIT, 22 patients allergic to BV were sting challenged. Only one (4.5%) patient had a mild objective SR.

CONCLUSIONS

The conventional 4- to 6-week MI can easily be extended to 3 months in most patients without any adverse events. MVIT given at a 3-month interval is safe and effective while being administered, as well as after its discontinuation. This fact should be applied to almost every patient allergic to insect venom.

Military trauma life support: a comprehensive training program for military physicians

The Israel Defense Forces Medical Corps prepares Israeli physicians for their field duty as providers of prehospital trauma care under combat conditions. Many physicians have no previous experience with emergency medicine. Military trauma education has been improving continuously to meet this challenge. In 1990, the Advanced Trauma Life Support program was launched in Israel. In 1998, a task-oriented approach to military trauma. Military Trauma Life Support, was introduced. This course is integrated in the 3-month training period of medical officers. Its objectives are to provide a comprehensive curriculum in prehospital military trauma, to simulate realistic combat scenarios and injury patterns, and to add practical skills and prehospital experience. The practical section includes definitive airway management in hospital operating rooms, emergency procedures training on cadavers, and prehospital experience on civilian emergency medical services ambulances.

Effects of growth factors on articular cartilage

Articular cartilage has limited intrinsic repair potential. The relative failure of many synthetic solutions has led to the growing interest in the development of cell-based repair systems for solving a number of clinical problems to articular cartilage. Many factors will dictate the success of these approaches, namely surgical technique and the repair method used, the patient's genetic make up and compliance with postoperative regimen.<br /> Many growth factors have been shown to have effects on chondrocytes and articular cartilage. Normal articular cartilage expresses insulin-like growth factor-I (IGF-I), basic fibroblast growth factor (bFGF) and transforming growth factor-b (TGFb) and these seem to be the most important local regulators of chondrocyte function. A complete understanding of the pathogenesis of osteoarthritis requires an understading of these growth factors. The role of cytokines and growth factors and the complex interactions that exist between them needs to be understood and at the moment our knowledge is incomplete. The advances of gene therapy however are promising and with further research patients may be offered not only a solution to their problem but also ways of preventing the disease in the first place.

Efficacy and safety of losartan/hydrochlorothiazide in patients with severe hypertension

This 12-week, open-label, multicenter study assessed the efficacy and safety of losartan/hydrochlorothiazide (HCTZ), alone or in combination with other antihypertensive agents, in the treatment of patients with severe systemic hypertension. Treatment began with once-daily losartan/HCTZ 50/12.5 mg. The dose was increased to 100/25 mg, if required, to achieve blood pressure (BP) control (sitting diastolic BP <95 mm Hg); felodipine (extended release) and/or atenolol could be added if target sitting diastolic BP was not achieved with losartan/HCTZ alone. Mean sitting systolic BP of the 131 patients enrolled was 165.3 mm Hg at baseline and 139.8 mm Hg at final visit (reduction -25.4 mm Hg; p < or =0.01). Mean sitting diastolic BP was 111.9 mm Hg at baseline and 93.6 mm Hg at final visit (reduction -18.4 mm Hg; p < or =0.01). After 2 weeks of treatment, 63.8% of patients (83 of 130) were taking losartan/HCTZ 50/12.5 mg alone. By the final visit, one third of patients (35.1%; 46/131) were still only taking losartan/HCTZ. Most patients (48.1%; 63 of 131) were taking losartan/HCTZ 100/25 mg plus felodipine (extended release) at the final visit. Losartan/HCTZ was well tolerated. Drug-related adverse experiences occurred in 30 patients (22.9%). Only 2 patients (1.5%) had a serious adverse experience; 6 patients (4.6%) discontinued the drug because of an adverse experience. In conclusion, losartan/ HCTZ, alone or as part of a regimen with other standard antihypertensive agents, is effective and well tolerated in the treatment of patients with severe hypertension.

Laryngeal preservation with supracricoid partial laryngectomy results in improved quality of life when compared with total laryngectomy

OBJECTIVES/HYPOTHESES

Study 1: To assess the oncologic outcome following supracricoid partial laryngectomy (SCPL). Study 2: To compare the quality of life (QOL) following SCPL to total laryngectomy (TL) with tracheoesophageal puncture (TEP). Study 3: To analyze whole organ TL sections to determine the percentage of lesions amenable to SCPL STUDY DESIGN: Study 1: A retrospective review of patients who underwent SCPL. Study 2: A non-randomized, prospective study using QOL instruments to compare patients who underwent either SCPL or TL Study 3: A retrospective histopathologic study of TL specimens assessed for the possibility of performing an SCPL.

METHODS

Study 1: Twenty-five patients with carcinoma of the larynx underwent SCPL between June 1992 and June 1999. Various rates of oncologic outcome were calculated. Study 2: Thirty-one patients participated in the QOL assessment. This included the SF-36 general health status measure, the University of Michigan Head and Neck Quality of Life (HNQOL) instrument, and the University of Michigan Voice-Related Quality of Life (VRQOL) instrument. Study 3: Ninety surgical specimens were obtained and studied from the total laryngectomy cases in the Tucker Collection. Multiple sites were evaluated for the presence of carcinoma A computer program was written to classify whether the patient was amenable to SCPL.

RESULTS

Study 1: The overall local control rate was 96% (24/25). The local control rate following SCPL with cricohyoidoepiglottopexy (CHEP) was 95% (20/21). The local control rate following SCPL with cricohyoidopexy (CHP) was 100% (4/4). Study 2: The SCPL had significantly higher domain scores than TL and TEP in the following categories for the SF-36: physical function, physical limitations, general health, vitality, social functioning, emotional limitations, and physical health summary. The significantly higher domains for the SCPL when compared with the TL and TEP for the HNQOL were eating and pain. Finally, when voice-related QOL was assessed with the V-RQOL, the domains of physical functioning and the total score were significantly better with SCPL when compared with TL and TEP. Study 3: Forty of 90 (44%) laryngeal whole organ specimens were determined to be resectable by SCPL. In 16 (18%) specimens, the patients could have undergone SCPL with CHEP and in 24 (27%) specimens the patients could have undergone SCPL with CHP. Among the 40 (44%) specimens determined to be able to have undergone SCPL, 19 were glottic (1 T1, 15 T2, 3 T3) and 21 were supraglottic (9 T2, 12 T3).

CONCLUSIONS

1) A review of the literature and an analysis of the data in this study indicate that excellent local control may be expected following SCPL. 2) The QOL following SCPL, as measured by three validated QOL instruments, is superior to TL with TEP. 3) A histologic assessment of whole organ sections of TL specimens indicates that many patients who have been subjected to TL may have been candidates for SCPL. 4) If the indications and contraindications are rigorously adhered to, SCPLs are reasonable alternatives to TL in selected cases.

Postmodern psychoanalysis

In keeping with the spirit of the postmodern, the author suggests that psychoanalysts should be wary of subscribing to a set of rules and/or a proper method for the conduct of psychoanalysis. He puts forward instead the suggestion that some patients do well with certain rules and not with others, and offers a brief report concerning a group of patients who were unable to 'live by the rules' to support such a viewpoint. He suggests that a corollary of this perspective is one that links the analyst's own capacity to live within or outside of rules to his or her effectiveness with these particular patients. From this unique illustrative group, the general conclusion is offered that only the singular goal of understanding in depth is the proper guiding rule of psychoanalysis.

Insect sting-inflicted systemic reactions: attitudes of patients with insect venom allergy regarding after-sting behavior and proper administration of epinephrine

BACKGROUND

Patients with insect venom allergy are at higher risk for development of a recurrent systemic reaction after re-sting. This risk significantly decreases with venom immunotherapy. Patients with insect venom allergy should be able to distinguish a life-threatening systemic reaction from all other various reactions after an insect sting. Accidental epinephrine injection by EpiPen has been reported in the past. Therefore patients with venom allergy should also be well trained in self-administration of their epinephrine when needed.

OBJECTIVE

Our objective was to assess patients' attitudes regarding after-sting behavior and their capability to correctly self-administer the epinephrine autoinjector.

METHODS

All patients with venom allergy attending our allergy unit either before commencement of or during venom immunotherapy answered a questionnaire addressing various aspects of their intended after-sting behavior. Using an EpiPen trainer device, patients' performance of EpiPen self-administration was evaluated.

RESULTS

Ninety-six patients participated in the study. Seventy-six of them were equipped with an EpiPen device. Less than 30% of these patients carried it at all times. After re-sting, 50 (54%) patients planned to wait for the development of other symptoms before taking any further action. Twenty-two percent of the patients said that after re-sting they would immediately administer their EpiPen. Proper EpiPen administration technique was demonstrated by 44% of the patients. Having not reached the maintenance dose correlated with a better compliance with carrying of the EpiPen. EpiPen instruction provided by an allergist correlated with a better EpiPen administration technique by the patients.

CONCLUSION

Many patients with venom allergy hold wrong ideas about after-sting behavior. Compliance with carrying EpiPen at all times and the ability to correctly administer it are both poor in most patients. Thorough and probably repeated instruction, both written and oral, provided by knowledgeable physicians is mandatory.

Pilot study of combined blockade of the renin-angiotensin system in essential hypertensive patients

BACKGROUND

Additive hemodynamic effects of combined blockade of the renin-angiotensin system by an angiotensin I converting enzyme inhibitor and an angiotensin II antagonist have been observed in sodium-depleted normotensive volunteers and in patients with congestive heart failure.

OBJECTIVE

To investigate whether the same additive hemodynamic effects occur in patients with hypertension and to verify the safety of such an approach.

DESIGN

Multicenter, randomized, double-blind, parallel-group, pilot study.

PATIENTS

177 patients with mild-to-moderate hypertension [diastolic blood pressure (DBP): 95-115 mmHg after a 4-week placebo run-in period] were included in the study.

INTERVENTION

Combination therapy consisting of 50 mg losartan daily and 10 mg enalapril daily was administered for 6 weeks. The effects of this therapeutic regimen was compared with similar groups of patients who received either 50 mg losartan daily or 10 mg enalapril daily.

MAIN OUTCOME MEASURES

24-hour ambulatory mean DBP and clinic DBP measured at trough after 6 weeks of treatment.

RESULTS

24-hour ambulatory mean DBP did not significantly differ between treatment groups although the combination tended to lower BP more. The combination therapy was more effective on clinic DBP measured at trough than was losartan by 3.2 mmHg [confidence interval (95%, CI) 0.7-5.7 mmHg, P = 0.012], and more effective than enalapril by 4.0 mmHg (95% CI, 1.5-6.4 mmHg, P = 0.002). In a subgroup of 28 patients, higher plasma active renin and angiotensin I levels during blockade by the combination therapy were observed. This finding confirmed that the combination of the two agents inhibited the renin-angiotensin system to a greater extent than did either agent alone.

CONCLUSION

A combination of 10 mg enalapril daily and 50 mg losartan daily safely induces a supplementary, although modest, fall in clinic DBP in patients with mild-to-moderate essential hypertension.

mu-opioid receptors are present in vagal afferents and their dendritic targets in the medial nucleus tractus solitarius

Ligands of the mu-opiate receptor (MOR) are known to influence many functions that involve vagal afferent input to the nucleus tractus solitarius (NTS), including cardiopulmonary responses, gastrointestinal activity, and cortical arousal. The current study sought to determine whether a cellular substrate exists for direct modulation of vagal afferents and/or their neuronal targets in the NTS by ligands of the MOR. Anterograde tracing of vagal afferents arising from the nodose ganglion was achieved with biotinylated dextran amine (BDA), and the MOR was detected by using antipeptide MOR antiserum. The medial subdivision of the intermediate NTS was examined by electron microscopy for the presence of peroxidase-labeled, BDA-containing vagal afferents and immunogold MOR labeling. MOR was present in both presynaptic axon terminals and at postsynaptic sites, primarily dendrites. In dendrites, MOR immunogold particles usually were located along extrasynaptic portions of the plasma membrane. Of 173 observed BDA-labeled vagal afferent axon terminals, 33% contained immunogold labeling for MOR within the axon terminal. Many of these BDA-labeled terminals formed asymmetric, excitatory-type synapses with dendrites, some of which contained MOR immunogold labeling. MORs were present in 19% of the dendrites contacted by BDA-labeled terminals but were present rarely in both the vagal afferent and its dendritic target. Together, these results suggest that MOR ligands modulate either the presynaptic release from or the postsynaptic responses to largely separate populations of vagal afferents in the intermediate NTS. These results provide a cellular substrate for direct actions of MOR ligands on primary visceral afferents and their second-order neuronal targets in NTS.

mu-Opioid receptors often colocalize with the substance P receptor (NK1) in the trigeminal dorsal horn

Substance P (SP) is a peptide that is present in unmyelinated primary afferents to the dorsal horn and is released in response to painful or noxious stimuli. Opiates active at the mu-opiate receptor (MOR) produce antinociception, in part, through modulation of responses to SP. MOR ligands may either inhibit the release of SP or reduce the excitatory responses of second-order neurons to SP. We examined potential functional sites for interactions between SP and MOR with dual electron microscopic immmunocytochemical localization of the SP receptor (NK1) and MOR in rat trigeminal dorsal horn. We also examined the relationship between SP-containing profiles and NK1-bearing profiles. We found that 56% of SP-immunoreactive terminals contact NK1 dendrites, whereas 34% of NK1-immunoreactive dendrites receive SP afferents. This result indicates that there is not a significant mismatch between sites of SP release and available NK1 receptors, although receptive neurons may contain receptors at sites distant from the peptide release site. With regard to opioid receptors, we found that many MOR-immunoreactive dendrites also contain NK1 (32%), whereas a smaller proportion of NK1-immunoreactive dendrites contain MOR (17%). Few NK1 dendrites (2%) were contacted by MOR-immunoreactive afferents. These results provide the first direct evidence that MORs are on the same neurons as NK1 receptors, suggesting that MOR ligands directly modulate SP-induced nociceptive responses primarily at postsynaptic sites, rather than through inhibition of SP release from primary afferents. This colocalization of NK1 and MORs has significant implications for the development of pain therapies targeted at these nociceptive neurons.

ET-1 in the myocardial interstitium: relation to myocyte ECE activity and expression

Increased plasma levels of endothelin-1 (ET-1) have been identified in congestive heart failure (CHF), but local myocardial interstitial ET-1 levels and the relation to determinants of ET-1 synthesis remain to be defined. Accordingly, myocardial interstitial ET-1 levels and myocyte endothelin-converting enzyme (ECE)-1 activity and expression with the development of CHF were examined. Pigs were instrumented with a microdialysis system to measure myocardial interstitial ET-1 levels with pacing CHF (240 beats/min, 3 wk; n = 9) and in controls (n = 14). Plasma ET-1 was increased with CHF (15 +/- 1 vs. 9 +/- 1 fmol/ml, P < 0.05) as was total myocardial ET-1 content (90 +/- 15 vs. 35 +/- 5 fmol/g, P < 0.05). Paradoxically, myocardial interstitial ET-1 was decreased in CHF (32 +/- 4 vs. 21 +/- 2 fmol/ml, P < 0.05), which indicated increased ET-1 uptake by the left ventricular (LV) myocardium with CHF. In isolated LV myocyte preparations, ECE-1 activity was increased by twofold with CHF (P < 0.05). In LV myocytes, both ECE-1a and ECE-1c mRNAs were detected, and ECE-1a expression was upregulated fivefold in CHF myocytes (P < 0.05). In conclusion, this study demonstrated compartmentalization of ET-1 in the myocardial interstitium and enhanced ET-1 uptake with CHF. Thus a local ET-1 system exists at the level of the myocyte, and determinants of ET-1 biosynthesis are selectively regulated within this myocardial compartment in CHF.

Multiple-dose efficacy and safety of an extended-release form of niacin in the management of hyperlipidemia

This multicenter trial evaluated the safety and efficacy of escalating doses of Niaspan (niacin extended-release tablets) and placebo (administered once-a-day at bedtime) in patients with primary hyperlipidemia on the percent change from baseline in levels of low-density lipoprotein (LDL) cholesterol and apolipoprotein B. Extended-release niacin was initiated at a dose of 375 mg/day, raised to 500 mg/day, and further increased in 500-mg increments at 4-week intervals to a maximum of 3,000 mg/day. A total of 131 patients (n = 87, extended-release niacin; n = 44, placebo) were treated for 25 weeks with study medication after a 6-week diet lead-in/drug washout phase and 2-week baseline LDL cholesterol stability phase. Significant decreases from baseline in levels of LDL cholesterol and apolipoprotein B became apparent with the 500-mg/day dose and were consistent at all subsequent doses (p < or =0. 05), reaching 21% and 20%, respectively, at the 3,000-mg/day dose. Significant increases from baseline in levels of high-density lipoprotein cholesterol became apparent with the 500-mg/day dose and were consistent at all subsequent doses (p < or = 0.05), reaching 30% at the 3,000-mg dose. Significant decreases from baseline in triglycerides and lipoprotein(a) occurred at the 1,000-mg dose and were apparent at all subsequent doses (p < or =0.05), reaching 44% and 26%, respectively, at the 3,000-mg dose. The most common adverse events were flushing and gastrointestinal disturbance. Transaminase increases were relatively small, and the proportion of patients who developed liver function abnormalities on extended-release niacin was not significantly different from placebo. Thus, extended-release niacin was generally well tolerated and demonstrated a dose-related ability to alter favorably most elements of the lipid profile.

Hyper-releasability of mast cells in family members of infants with sudden infant death syndrome and apparent life-threatening events

BACKGROUND

An allergic reaction with increased degranulation of mast cells has been suggested as a possible mechanism in sudden infant death syndrome (SIDS).

STUDY DESIGN

Mast cell releasability was assessed in 2 study groups: A, 22 subjects, 16 first-degree relatives of infants who had had an apparent life-threatening event (ALTE) and 6 infants after ALTE and B, 46 first-degree relatives of SIDS cases. These groups were compared with 71 members of an age-matched control group. In each subject the skin wheal and flare reactions were measured after an intradermal injection of 0.02 mL of each of the following substances dissolved in phenol-saline solution: histamine 0.0001 mg/mL, histamine 0.001 mg/mL, codeine 0.5 mg/mL, codeine 1 mg/mL, compound 48/80 0.05 mg/mL, compound 48/80 0. 1 mg/mL, and phenol-saline solution. The size of wheal and flare skin reaction was assessed by computerized planimetry after the shape of the cutaneous response was copied onto a paper.

RESULTS

The wheal and flare skin reaction to each of the substances was significantly larger in the 2 study groups compared with the control group (P <.05) except for the wheal reaction to compound 48/80 0.1 mg/mL, codeine 0.5 mg/mL, and histamine in both concentrations for group A and the wheal reaction to codeine 1 mg/mL and histamine in both concentrations for group B. All individuals with increased reaction belonged to 3 (50%) of 6 families with ALTE history and to 8 (73%) of 11 families with SIDS history.

CONCLUSIONS

Increased mast cell hyper-releasability and degranulation take place in family members of some SIDS and ALTE cases and in some infants with ALTE, supporting a possible role for an immunologic mechanism in the pathophysiology of these entities.

Rapid degradation of an abnormal protein in Escherichia coli proceeds through repeated cycles of association with GroEL

Molecular chaperones are necessary for the breakdown of many abnormal proteins, but their functions in this process have remained obscure. The rapid degradation of the abnormal fusion protein CRAG in Escherichia coli requires the molecular chaperones GroEL, GroES, and trigger factor and proceeds through the formation of a CRAG-GroEL-trigger factor complex. Also associated with GroEL are smaller discrete fragments of CRAG. Pulse-chase experiments showed that these fragments were short-lived intermediates in CRAG degradation formed by C-terminal cleavages. Thus, CRAG degradation is not highly processive. In cells lacking the ClpP protease, the generation of these fragments and their subsequent degradation were much slower than in the wild type. Dissociation of CRAG from GroEL was necessary for its digestion by the ClpP protease, because in a groES temperature-sensitive mutant, CRAG was stable and accumulated on GroEL. Furthermore, the expression of a dominant GroEL mutant defective in substrate dissociation slowed degradation of both CRAG and the fragments. Therefore, we suggest that CRAG degradation proceeds through multiple rounds of substrate binding to GroEL, followed by their GroES-dependent dissociation, which allows further digestion by the protease. In this multistep process, GroEL and GroES function repeatedly, apparently to allow further degradation of CRAG and its fragments by the protease.