Effect of phrenic afferent stimulation on pattern of respiratory muscle activation

Ventilation and electromyogram (EMG) activities of the right hemidiaphragm, parasternal intercostal, triangularis sterni, transversus abdominis, genioglossus, and alae nasi muscles were measured before and during central stimulation of the left thoracic phrenic nerve in 10 alpha-chloralose anesthetized vagotomized dogs. Pressure in the carotid sinuses was fixed to maintain baroreflex activity constant. The nerve was stimulated for 1 min with a frequency of 40 Hz and stimulus duration of 1 ms at voltages of 5, 10, 20, and 30 times twitch threshold (TT). At five times TT, no change in ventilation or EMG activity occurred. At 10 times TT, neither tidal volume nor breathing frequency increased sufficiently to reach statistical significance, although the change in their product (minute ventilation) was significant (P less than 0.05). At 20 and 30 times TT, increases in both breathing frequency and tidal volume were significant. At these stimulus intensities, the increases in ventilation were accompanied by approximately equal increases in the activity of the diaphragm, parasternal, and alae nasi muscles. The increase in genioglossus activity was much greater than that of the other inspiratory muscles. Phrenic nerve stimulation also elicited inhomogeneous activation of the expiratory muscles. The transversus abdominis activity increased significantly at intensities from 10 to 30 times TT, whereas the activity of the triangularis sterni remained unchanged. The high stimulation intensities required suggest that the activation of afferent fiber groups III and IV is involved in the response. We conclude that thin-fiber phrenic afferent activation exerts a nonuniform effect on the upper airway, rib cage, and abdominal muscles and may play a role in the control of respiratory muscle recruitment.

Quantitative assessment of bed rise difficulty in young and elderly women

OBJECTIVE

To describe the motions which occur during rising from bed, specifically the motions that appeared to characterize difficulty in rising from a bed in older adults.

DESIGN

Development of a Mobility assessment tool.

SETTING

Retirement center and two university laboratories.

PARTICIPANTS

Three groups of female volunteers: young controls (n = 17, mean age 24), community-dwelling older adults (n = 12, mean age 71), and retirement center-dwelling older adults who admitted to difficulty in rising from a bed (n = 15, mean age 86).

INTERVENTION

Videotaping of motions occurring during controlled rises from a supine to sitting position.

MAIN OUTCOME MEASURES

These motions were rated on the specially developed Bed Rise Difficulty (BRD) scale, a scale designed to measure movements that characterize difficulty in rising from a bed in older adults. Subject groups were compared in total BRD score, individual BRD item score, and total time to rise. Item relationships and scale reliability were also assessed.

RESULTS

Older adults with no apparent difficulty in rising based on total time to rise or on the BRD score nevertheless showed differences in upper extremity use when compared to young controls. Older adult subjects with difficulty in rising from a bed, when compared to other older adults with no apparent difficulty, differed more often in their upper extremity and leg use to facilitate the rise. Five BRD scale items, including use of extremity pushes, discontinuity of trunk and leg motion, multiple shoulder/pelvic adjustments, multiple leg adjustments, and poor vertical heel clearance may have best indicated true bed rise difficulty.

CONCLUSIONS

These data provide a reliable and valid method to characterize difficulty in rising from a bed and provide the basis for biomechanical analyses of the strength and joint ranges of motion required to rise from a bed.

Survey of 3765 cardiopulmonary resuscitations in British hospitals (the BRESUS Study): methods and overall results

OBJECTIVE

To determine the circumstances, incidence, and outcome of cardiopulmonary resuscitation in British hospitals.

DESIGN

Hospitals registered all cardiopulmonary resuscitation attempts for 12 months or longer and followed survival to one year.

SETTING

12 metropolitan, provincial, teaching, and non-teaching hospitals across Britain.

SUBJECTS

3765 patients in whom a resuscitation attempt was performed, including 927 in whom the onset of arrest was outside the hospital.

MAIN OUTCOME MEASURE

Survival after initial resuscitation, at 24 hours, at discharge from hospital, and at one year, calculated by the life table method.

RESULTS

There were 417 known survivors at one year, with 214 lost to follow up. By life table analysis for every eight attempted resuscitations there were three immediate survivors, two at 24 hours, 1.5 leaving hospital alive, and one alive at one year. Survival at one year was 12.5% including out of hospital cases and 15.0% not including these cases. Each hospital year averaged 30 survivors at one year: three who had an arrest outside hospital, seven who had one in the accident and emergency department, seven in the cardiac care unit, 10 in the general wards, and three in other, non-ward areas. Within the hospitals survival rates were best in those who had an arrest in the accident and emergency department, the cardiac care unit, or other specialised units. Outcome varied 12-fold in subgroups defined by age, type of arrest, and place of arrest.

CONCLUSION

71% of the mortality at one year in patients undergoing attempted resuscitation occurred during the initial arrest. Hospital resuscitation is life saving and cost effective and warrants appropriate attention, training, coordination, and equipment.

Oxygen delivery-independent effect of blood flow on diaphragm fatigue

To determine the effect of blood flow on diaphragm fatigue independent of oxygen delivery, the left hemidiaphragm was vascularly isolated in 14 pentobarbital-anesthetized, mechanically ventilated dogs. Fatigue (decline in tension generation) of the left diaphragm was induced by phrenic nerve stimulation at 10 Hz, 12/min, duty cycle of 0.5 for 8 min. Two stimulation periods separated by 30 min of rest were performed in each animal. Diaphragmatic O2 delivery during the two periods was the same. In Group 1 (n = 8), the diaphragm was autoperfused from the femoral artery (high O2-low flow) during the first stimulation period. The tension generated by the diaphragm during this period declined progressively to 47.7% of initial values. In the second period in this group, the diaphragm was pump perfused with arterial blood, diluted with an equal volume of 6% dextran at a flow rate twice that of the first period (low O2-high flow). Tension in this period declined to 76% of initial tension (p less than 0.05 compared with high O2-low flow). In Group 2 (n = 6), stimulation performed while perfusing the diaphragm in the first period with diluted arterial blood at a flow rate twice that recorded during autoperfusion (low O2-high flow) produced a decline in tension to 70% of the initial values. In the second period, the diaphragm was perfused with undiluted arterial blood at a flow rate equal to 50% of that of the first period (high O2-low flow). Tension during this period declined to 56% of initial values (p less than 0.05 compared with low O2-high flow).(ABSTRACT TRUNCATED AT 250 WORDS)

Ventilatory effects of the interaction between phrenic and limb muscle afferents

We studied the effects on ventilation and ventilatory muscle activation of stimulation of the central ends of the left phrenic and gastrocnemius nerves separately and concurrently in 10 spontaneously breathing, alpha-chloralose anaesthetized dogs. The nerves were stimulated for 1 min, at a frequency of 40 Hz and pulse duration of 1 ms. The phrenic nerve was stimulated at 20 and 40 times twitch threshold (TT). During these stimulation periods ventilation increased by 39% and 79% of control values, respectively. The gastrocnemius nerve was stimulated at 20 times TT. This produced a 90% increase in ventilation. Stimulation of either nerve resulted in increases in the activity of the right diaphragm, parasternal intercostal and alae nasi muscles comparable in magnitude to the increase in tidal volume. The activities of the genioglossus and transversus abdominis muscle increased to a much greater extent than did the other muscles under all conditions. In contrast, triangularis sterni activity remained unchanged during stimulation of either nerve. The phrenic nerve was then stimulated at 40 times TT for 1 min with superimposed gastrocnemius nerve stimulation (20 times TT) during the last 30 s. Ventilation had risen by 66% after 30 s of phrenic nerve stimulation. With the addition of gastrocnemius nerve stimulation, ventilation rose by a further 84% for a total increase of 150% of the control value. Mathematical summation of the responses to individual nerve stimulation at these intensities predicted a 156% increase in ventilation. Similar degrees of summation were found with respect to respiratory muscle activation. We conclude that the interaction between phrenic and limb muscle (gastrocnemius) afferent is additive with respect to their effects on ventilation.

A longitudinal study of trachoma in a Gambian village: implications concerning the pathogenesis of chlamydial infection

In order to investigate risk factors for the acquisition of trachoma, and to study the effect of continued exposure to ocular chlamydial infection on the severity of inflammatory trachoma and its cicatricial sequelae, a longitudinal study was conducted in a Gambian village. Over a 20-month period, the incidence of active (inflammatory) trachoma was significantly higher among those sharing a bedroom with an active case (64/561, 11.4%) than among those who were not exposed in this way (37/658, 5.6%) (relative risk 1.97, 95% confidence interval 1.33-2.90). There was a positive trend in the odds ratio for severe to moderate inflammatory disease versus mild disease as the number of active cases in the bedroom increased, but this failed to achieve statistical significance (P = 0.0506). Individuals with inflammatory trachoma of moderate or severe intensity at one survey were significantly more likely than others to have moderate or severe inflammatory changes at a previous or subsequent survey (odds ratio 14.9, 95% confidence interval 3.9-68.0), implying that host factors may be more important determinants of severity than the frequency of exposure to reinfection.

Analysis of human chest wall motion using a two-compartment rib cage model

We present a model of chest wall mechanics that extends the model described previously by Macklem et al. (J. Appl. Physiol. 55: 547-557, 1983) and incorporates a two-compartment rib cage. We divide the rib cage into that apposed to the lung (RCpul) and that apposed to the diaphragm (RCab). We apply this model to determine rib cage distortability, the mechanical coupling between RCpul and RCab, the contribution of the rib cage muscles to the pressure change during spontaneous inspiration (Prcm), and the insertional component of transdiaphragmatic pressure in humans. We define distortability as the relationship between distortion and transdiaphragmatic pressure (Pdi) and mechanical coupling as the relationship between rib cage distortion and the pressure acting to restore the rib cage to its relaxed configuration (Plink), as assessed during bilateral transcutaneous phrenic nerve stimulation. Prcm was calculated at end inspiration as the component of the pressure displacing RCpul not accounted for by Plink or pleural pressure. Prcm and Plink were approximately equal during quiet breathing, contributing 3.7 and 3.3 cmH2O on average during breaths associated with a change in Pdi of 3.9 cmH2O. The insertional component of Pdi was measured as the pressure acting on RCab not accounted for by the change in abdominal pressure during an inspiration without rib cage distortion and was 40 +/- 12% (SD) of total Pdi. We conclude that there is substantial resistance of the human rib cage to distortion, that, along with rib cage muscles, contributes importantly to the fall in pleural pressure over the costal surface of the lung.

Vector analysis in partitioning of inspiratory muscle action in dogs

We considered the displacements and the pressure changes resulting from isolated contraction of 2 muscles as analogous to 2 vectors and those during simultaneous contraction as resultants. These were resolved into contributing components to calculate the contribution of each muscle group and partition the action of inspiratory muscles. Relative displacements of rib cage (delta RC) and abdomen (delta AB) and changes in transpulmonary (delta PL) and abdominal (delta Pab) pressures were obtained during spontaneous breathing, isolated contraction of rib cage muscle (RCM), diaphragmatic (DI), costal and crural diaphragm and passive inflation in 7 dogs. The diaphragm accounted for 58 +/- 19.8% SD of the chest wall displacement and 90 +/- 6.6% SD of the pressure swings during spontaneous breathing. The costal diaphragm accounted for 61 +/- 28.9% SD of the displacement produced by contraction of the entire diaphragm. Despite wide variability in the action of the diaphragm and its components, all animals breathed close to their relaxation characteristic. We conclude that there are marked differences in the degree of RCM recruitment between dogs in order to prevent chest wall distortions.

Vector analysis in partitioning of inspiratory muscle action in dogs

We considered the displacements and the pressure changes resulting from isolated contraction of 2 muscles as analogous to 2 vectors and those during simultaneous contraction as resultants. These were resolved into contributing components to calculate the contribution of each muscle group and partition the action of inspiratory muscles. Relative displacements of rib cage (delta RC) and abdomen (delta AB) and changes in transpulmonary (delta PL) and abdominal (delta Pab) pressures were obtained during spontaneous breathing, isolated contraction of rib cage muscle (RCM), diaphragmatic (DI), costal and crural diaphragm and passive inflation in 7 dogs. The diaphragm accounted for 58 +/- 19.8% SD of the chest wall displacement and 90 +/- 6.6% SD of the pressure swings during spontaneous breathing. The costal diaphragm accounted for 61 +/- 28.9% SD of the displacement produced by contraction of the entire diaphragm. Despite wide variability in the action of the diaphragm and its components, all animals breathed close to their relaxation characteristic. We conclude that there are marked differences in the degree of RCM recruitment between dogs in order to prevent chest wall distortions.

The role of Chlamydia trachomatis and Neisseria gonorrhoeae in the aetiology of ectopic pregnancy in Gabon

OBJECTIVE

To study the association between ectopic pregnancy and Chlamydia trachomatis and Neisseria gonorrhoeae.

DESIGN

A prospective observational study with two comparison groups.

SETTING

A general hospital in Franceville, Gabon.

SUBJECTS

Forty-five women with ectopic pregnancies and two comparison groups each of 45 women, one at 5 to 12 and the other at 32 to 41 weeks gestation.

MAIN OUTCOME MEASURES

Serum levels of IgG and IgA antibodies to C. trachomatis (L1 and rMOMP) and N. gonorrhoeae (pili) in all the women. In the women with ectopic pregnancy peritoneal adhesions were scored and in 40 women samples of tube were cultured for organisms being studied.

RESULTS

IgG and IgA antibodies to C. trachomatis (L1) were detected in 84% of the ectopic group and 53 and 39% of the comparison groups (P less than 0.0001). IgG and IgA antibodies to N. gonorrhoeae occurred in 49, 28 and 18% and 49, 28 and 26% of the groups but the differences were not statistically significant. Adhesions were positively associated with the antibodies. C. trachomatis was cultured from the tubes of 71% of the women with ectopic pregnancy.

CONCLUSIONS

Infection with chlamydia, and probably with N. gonorrhoeae, is an important factor in the causation of ectopic pregnancy in Gabon.

Chlamydia trachomatis major outer membrane protein epitopes expressed as fusions with LamB in an attenuated aro A strain of Salmonella typhimurium; their application as potential immunogens

The major outer-membrane protein (MOMP) of Chlamydia trachomatis is the focus of attention for chlamydial vaccine design, particularly those serovar- and subspecies-specific epitopes which provoke neutralizing immune responses. Selected surface-exposed B-cell epitopes of MOMP, incorporating B-subspecies specificities, were expressed as fusions with LamB, an inducible outer-membrane transport protein of Escherichia coli. These recombinant chlamydial-LamB proteins were correctly transported to the outer membrane of both E. coli and an aro A mutant of Salmonella typhimurium. The immunogenicity of the constructs was investigated in a mouse model of chlamydial salpingitis. After oral immunization, recombinant S. typhimurium were recovered from the livers of mice for up to two weeks, and a serum IgG response was induced both to the Salmonella and to the inserted chlamydial epitopes. By contrast, intravenous inoculation was ineffective. Although these LamB fusions proved only weakly immunogenic, this approach should be useful for investigating the ability of attenuated S. typhimurium vaccines incorporating chlamydial epitopes to stimulate protective mucosal immunity in the mouse model of chlamydial salpingitis.

Respiratory muscle activation by limb muscle afferent stimulation in anesthetized dogs

In 10 chloralose anaesthetized and spontaneously breathing dogs, we assessed the effect of limb muscle afferents on the peak integrated EMG activities of the genioglossus, alae nasi, costal diaphragm, parasternal intercostal, triangularis sterni, and transverse abdominis muscles. The influence of vagal and baroreceptor afferents were eliminated by vagotomy and perfusion of carotid sinuses at a constant pressure. Muscle afferents were activated by stimulating the central end of the gastrocnemius nerve for 1 min at 40 Hz and at different voltages. Stimulation at voltages equal to 5, 10 and 20 times twitch-threshold increased minute ventilation to 165, 216 and 250% of pre-stimulation values, respectively, which was achieved by increasing breathing frequency (shortening of the inspiratory and expiratory times) and tidal volume. The activity of the parasternal intercostal and alae nasi muscles increased by a similar degree to that of the diaphragm while the activities of the genioglossus and transverse abdominis were augmented to a greater degree than that of the diaphragm. On the other hand, the motor drive to triangularis sterni increased significantly only at 20 times twitch-threshold and to a lesser degree than that to the diaphragm. These results suggest that upper airway, inspiratory and expiratory rib cage and abdominal muscles may be independently regulated. Differences in the sensitivity of these muscles to the activation of limb muscle afferents can be explained by a complex pattern of central projections of these afferents on the central respiratory controllers or by intrinsic properties of the motor output of these controllers.

Expression of MHC class II antigens by conjunctival epithelial cells in trachoma: implications concerning the pathogenesis of blinding disease

In an attempt to understand the pathogenesis of corneal changes and conjunctival scarring in trachoma, which are responsible for blindness in some 7 million people worldwide, the surface expression of major histocompatibility complex class II antigens on conjunctival epithelial cells was sought in patients with different clinical features of the disease. Class II expression was significantly associated with active (inflammatory) trachoma, but an independent association with corneal pannus or conjunctival scarring could not be shown. Longitudinal data suggest that class II expression may antedate clinically active disease and persist after it has resolved.

Hemodynamic effects of lobar pulmonary artery occlusion in a porcine sepsis model

We induced severe pulmonary hypertension and acute lung injury in 6 pigs by Pseudomonas aeruginosa infusion. We studied the effect of pulmonary artery catheter inflation of a pulmonary artery catheter balloon in the left lower lobar pulmonary artery was accompanied by a significant (p less than 0.05, paired t test) increase in pulmonary artery pressure, a decrease in left atrial pressure, a decrease in cardiac output, and a decrease in mean arterial pressure. No significant changes occurred when the catheter was advanced into the wedged position without balloon inflation. Balloon inflation had no significant effect on these variables before bacterial infusion. We conclude that with sufficiently severe pulmonary hypertension in association with diffuse lung injury, lobar pulmonary artery occlusion may cause alterations in cardiac output and left atrial pressure. This may confuse interpretation of pulmonary artery catheter measurements.

Nucleotide sequence and taxonomic value of the major outer membrane protein gene of Chlamydia pneumoniae IOL-207

Chlamydia pneumoniae IOL-207 genomic DNA was hybridized with a 1.5 kb labelled DNA probe containing the 3' region of the coding sequence for the major outer membrane protein (MOMP) of C. trachomatis serovar L1. An 8.5 kb Bg/II fragment containing the complete MOMP gene was cloned into lambda EMBL3. Two hybridizing EcoRI fragments were sub-cloned into the lambda ZAP II cloning vector and the resulting plasmids were used as templates for sequencing both strands of the C. pneumoniae MOMP gene. Computer taxonomic studies using the nucleotide and inferred amino acid sequence of the MOMP of C. pneumoniae IOL-207 and all known chlamydial MOMP sequences supported the designation of C. pneumoniae as a new species, but electron microscope studies suggested that the presence of pear-shaped elementary bodies (EBs) may not be a reliable taxonomic criterion.

Isolation of recombinant fragments of the major outer-membrane protein of Chlamydia trachomatis: their potential as subunit vaccines

Recombinant fragments of the major outer-membrane protein (MOMP) of Chlamydia trachomatis, expressed at high levels in Escherichia coli, were isolated and purified. Antisera to the recombinant proteins reacted preferentially with overlapping synthetic peptides covering the immunoaccessible variable segments of MOMP. These sera also reacted in a species-specific manner with the surface of intact infectious elementary bodies, and in a Chlamydia genus-specific manner in assays using denatured or bound chlamydial antigens. The ability of recombinant MOMP preparations to elicit antibody to the surface of chlamydial elementary bodies raises the possibility that these proteins may be useful for chlamydial vaccine development.

The major outer-membrane proteins of Chlamydia trachomatis serovars A and B: intra-serovar amino acid changes do not alter specificities of serovar- and C subspecies-reactive antibody-binding domains

The major outer-membrane protein (MOMP) of Chlamydia trachomatis is a promising candidate antigen for chlamydial vaccine development. We have sequenced the MOMP genes for a serovar A and a serovar B isolate and have compared these new sequences with those already reported. Intra-serovar changes in the inferred amino acid sequences of the surface-exposed variable segments known to be responsible for binding of neutralizing antibody were observed. Nevertheless, epitope mapping with solid-phase peptides showed that these intra-serovar changes did not affect the binding of serovar- and subspecies-specific, potentially protective antibodies. Variable segment 1 of C. trachomatis serovar A contained two adjacent antibody-binding sites, one of which was C-subspecies specific while the other was serovar A specific. Therefore the subspecies binding site for C-complex organisms is in variable segment 1, whilst that for B-complex organisms is in variable segment 4. This work shows that MOMP sequences are relatively stable within the serovar categorization for isolates taken decades apart from different continents. Within a given serovar, however, limited interchange of functionally related amino acids may occur without impairing the binding of serovar-specific antibody.

Respiratory muscle incoordination in stuttering speech

We investigated the role of respiratory muscle incoordination during stuttering by measuring esophageal, gastric, and transdiaphragmatic pressures to obtain subglottic pressure (Psg) and indices of diaphragmatic, rib cage, and abdominal muscle contraction during speech in normal volunteers and in severe stutterers. We found in contrast to the relatively constant subglottic pressure during normal conversational speech that speech in stutterers was characterized by failure to control Psg because of contraction of the diaphragm, rib cage, and abdominal muscles singly or in various combinations. As a result, Psg varied substantially and sometimes chaotically from too high to too low, rendering normal speech impossible. During periods of fluency, Psg was much better controlled. We conclude that incoordination of the respiratory muscles is a major problem in stuttering, resulting in failure to control the pressure difference across the vocal cords. It is unclear if this is a primary abnormality or is a secondary response to a primary abnormality elsewhere.

Two cases of barotrauma associated with transtracheal jet ventilation

Two patients suffered barotrauma whilst undergoing transtracheal jet ventilation (TTJV). In the first, TTJV was provided by a Sanders injector and in the second it was given by a high frequency jet ventilator. Barotrauma was a consequence of the expiratory pathway becoming blocked. The mechanism of barotrauma and a method of airway pressure monitoring during TTJV are discussed. It is recommended that meticulous care is taken to ensure an adequate path for expiration when jet ventilation is used.

Sulfur-rich proteins of Chlamydia trachomatis: developmentally regulated transcription of polycistronic mRNA from tandem promoters

RNA was extracted at various times from cells infected with Chlamydia trachomatis serovar L1. Northern-blot analysis showed that transcription of the CrP gene encoding the 60-kDa cysteine-rich outer membrane protein (CrP) produces a temporally controlled polycistronic mRNA. Primer extension analysis indicated the presence of tandem promoters separated by 66 nt with transcriptional start points (tsp) located 577 and 643 nt upstream from the start codon of the mature 60-kDa CrP. Nucleotide (nt) sequencing of this region revealed a small open reading frame (SORF) with coding potential for an 88-amino acid protein containing 13 cysteine residues. This SORF is transcribed as both a polycistronic 2300-nt mRNA together with the CrP gene, and as a separate 480-nt mRNA. Analysis of the upstream sequences, around the tsp for these mRNAs, revealed the presence of three inverted repeat structures that might act as binding domain(s) for a regulatory protein.

Capital management balances charitable, financial goals

Effective capital management allows not-for-profit healthcare organizations to make investment decisions that fulfill their missions and meet financial goals. The process involves identifying components of the hospital's value and creating policies aimed at maximizing it; determining the hospital's ability to produce financial capital; and developing a process for allocating this financial capability among the components of value. Once this is completed, hospitals should determine criteria that balance charitable and financial goals, enabling them to pursue sound investments.

Correlation of infertility with altered tubal morphology and function in mice with salpingitis induced by a human genital-tract isolate of Chlamydia trachomatis

Progesterone-treated C3H mice were inoculated into the uterus or ovarian bursa with a human genital tract isolate of C. trachomatis (serovar E), or with control medium alone. The mice were then observed at various times up to 260 days after inoculation. Before being killed the mice were given pituitary gonadotrophins to induce ovulation. Eggs were sought in the oviducts and ciliary activity in the fimbrial and ampullary sections of the oviducts was determined by light microscopy, before detailed examination by scanning electron microscopy. Eggs were visible in all control oviducts and both mucosal ultrastructure and ciliary activity appeared normal. By contrast, eggs were not recovered from the inoculated oviducts of mice infected intrabursally, nor was ciliary activity observed up to 28 days after inoculation. After this, ciliary activity reappeared but eggs were still not transported to the oviduct. Ultrastructural studies suggested that severe mucus congestion accompanied by tubal oedema and loss of ciliated epithelia play a major role in the aetiology of chlamydial-induced tubal damage. Infertility following chlamydial salpingitis could be associated with failure of egg transportation to the oviduct. Egg transport was still impaired even when luminal ciliary activity, ultrastructural integrity and patency had recovered. Our results suggest that chlamydial salpingitis in this mouse model closely resembles the human disease in its pathology and consequences for fertility, making the model particularly relevant for research on chlamydial vaccine development.