Risk factors for COVID-19 mortality in hospitalized patients in Bolivia.

Objectives: This study aimed to ascertain which factors are associated with higher risk of mortality among hospitalized COVID-19 Bolivian patients. Methods: This retrospective observational study assessed risk factors associated with mortality in patients (n = 549) hospitalized for SARS-CoV-2 infection in a Bolivian hospital between April 6, 2020, and August 18, 2022. Results: The results provide evidence of association between male sex (odds ratio [OR] = 1.6, 95% confidence interval [CI] 1.06-2.6), older age, 51-61 years-old (OR = 5.2, 95% CI 2.2-12.6), 62-70 years-old (OR = 8.7, 95% CI 3.7-20.5), >70 years-old (OR = 16.9, 95% CI 7.1-39.9), and blood group A (OR = 1.9, 95% CI: 1.1-3.4) with higher mortality risk. The strong association between mortality and relatively young age, may be due to high frequency of undiagnosed comorbidities. Vaccination was associated with a reduction in mortality only when time period of hospitalization was not adjusted for. Conclusion: Among hospitalized patients in Bolivia male sex, older age, and blood group A are associated with higher mortality risk. Mortality risk increased markedly from a relatively young age and decreased in parallel to the uptake of the vaccination program. However, the gradual reduction in mortality can also be due to improved patient management and changes in natural immunity and virulence of circulating strains as the pandemic progressed.

Morphological Assessment of Concomitant Lesions Detected in Goat Herds Naturally Infected with Paratuberculosis (Johne's Disease).

Paratuberculosis (PTB), caused by Mycobacterium avium subspecies paratuberculosis (MAP), causes significant financial losses in the ruminant industry. The aim of this study is to describe the concomitant pathological findings as well as PTB-induced lesions in 39 naturally infected goats (15 vaccinated and 24 non-vaccinated). All animals exhibited MAP-induced microscopic lesions affecting target organs, although only 62% of those were detected grossly. Mainly concomitant inflammatory pathologies were recognized affecting the hemolymphatic, respiratory and gastrointestinal systems. Non-vaccinated animals exhibited both moderate and marked granulomatous enteritis in contrast with vaccinated ones which presented mild intestinal affection. Our results demonstrate that non-vaccinated animals presented pneumonia in all age groups studied (from 12 up to >48 months old). A significantly higher prevalence of ileocecal valve PTB lesions was detected in non-vaccinated animals with pneumonic lesions (p = 0.027). Furthermore, a reduction of gastrointestinal non-PTB processes was described in vaccinated goats. In conclusion, a PTB infected goat herd can be affected by a wide range of concomitant pathologies, mostly inflammatory in origin. Anatomic pathology is of crucial importance for correct herd diagnosis and histopathology is an indispensable tool for lesion detection. Additionally, anti-MAP vaccination could have a beneficial effect on the reduction of respiratory and gastrointestinal non-PTB diseases.

Intralesional Meglumine Antimoniate: Safe, Feasible and Effective Therapy for Cutaneous Leishmaniasis in Bolivia.

The standard of care for cutaneous leishmaniasis includes the intramuscular/intravenous administration of pentavalent antimonials that are toxic and poorly tolerated. Primary health care usually lacks trained health staff for the diagnosis and treatment of leishmaniasis in Cochabamba Bolivia. Taking these aspects into account, a Bolivian consortium set out to explore the intralesional administration of meglumine antimoniate to treat cutaneous leishmaniasis during primary care under programmatic conditions. A four-step strategy consisting of clinical training for intralesional treatment and the promotion and periodic follow-up of health staff was carried out. The training process was applied in situ to personnel of nine primary health care centres. The intralesional treatment was applied five times every other day. Clinical follow-up after six-months of treatment showed a 77% healing proportion and 5% of therapeutic failure among 152 enrolled patients. The drug volume used in the intralesional procedure was on average 1.7 mL/ulcer treated. In conclusion, the strategy used was successful and effective, accomplishing a healing proportion similar to the long standardized treatment with a reduced time of administration, no severe side effects, and it is feasible to conduct by trained health staff. Our study supports the current PAHO/WHO recommendation for the intralesional administration of pentavalent antimonials for the treatment of cutaneous leishmaniasis.

Morphological Structure of the Aortic Wall in Deep Diving Cetacean Species: Evidence for Diving Adaptation.

This study analyses the aortic wall structure in nine cetacean species with deep diving habits belonging to four Odontoceti families: Ziphiidae, Kogiidae, Physteridae, and Delphinidae. Samples of ascending, thoracic and abdominal aorta were processed for histological and morphometric studies. The elastic component was higher in the proximal aortic segments, and the muscular elements increased distally in all cases. Morphometric analyses showed that all families presented a decrease in the thickness of the arterial wall and the tunica media along the aorta. The reduction was dramatic between ascending and thoracic aorta in the Physeteridae specimens; meanwhile, the other three families showed a more uniform decrease between the ascending, thoracic and abdominal aorta. The decline was not correlated with a reduced elastic or lamellar unit thickness but with a loss of lamellar units. The organization of the elements in the aortic wall did not show essential modifications between the four families, resembling the structure described previously in the shallow and intermediate diving dolphins. Our findings support that the difference in the morphometric characteristics of the different segments in the aortic wall is likely related to the diving habit more than the absolutes values of any other parameter.

Budd-Chiari-like pathology in dolphins.

Nearly two decades ago, pathologic examination results suggested that acoustic factors, such as mid-frequency active naval military sonar (MFAS) could be the cause of acute decompression-like sickness in stranded beaked whales. Acute systemic gas embolism in these whales was reported together with enigmatic cystic liver lesions (CLL), characterized by intrahepatic encapsulated gas-filled cysts, tentatively interpreted as "gas-bubble" lesions in various other cetacean species. Here we provide a pathologic reinterpretation of CLL in odontocetes. Among 1,200 cetaceans necropsied, CLL were only observed in four striped dolphins (Stenella coeruleoalba), with a low prevalence (2%, N = 179). Together, our data strongly suggest that CLL are the result of the combination of a pre-existing or concomitant hepatic vascular disorder superimposed and exacerbated by gas bubbles, and clearly differ from acute systemic gas embolism in stranded beaked whales that is linked to MFAS. Budd-Chiari-like syndrome in dolphins is hypothesized based on the present pathologic findings. Nonetheless, further researched is warranted to determine precise etiopathogenesis(es) and contributing factors for CLL in cetaceans.

Cetaceans Humerus Radiodensity by CT: A Useful Technique Differentiating between Species, Ecophysiology, and Age.

Cetaceans are mammals that underwent a series of evolutionary adaptations to live in the aquatic environment, including morphological modifications of various anatomical structures of the skeleton and their bone mineral density (BMD); there are few studies on the latter. BMD is related to the radiodensity measured through computed tomography (CT) in Hounsfield units (HU). This work aimed to test and validate the usefulness of studying humeral bone radiodensity by CT of two cetacean species (the Atlantic spotted dolphin and the pygmy sperm whale) with different swimming and diving habits. The radiodensity was analysed at certain levels following a new protocol based on a review of previous studies. Humeral radiodensity values were related to four aspects: species, diving behaviour, swimming activity level, and age. We observed that the consistent differences in the radiodensity of the cortical bone of the distal epiphysis between animals of different life-history categories suggest that this bone portion could be particularly useful for future ontogenetic studies. Hence, this technique may be helpful in studying and comparing species with different ecophysiologies, particularly distinguishing between swimming and diving habits.

Methodology and Neuromarkers for Cetaceans' Brains.

Cetacean brain sampling may be an arduous task due to the difficulty of collecting and histologically preparing such rare and large specimens. Thus, one of the main challenges of working with cetaceans' brains is to establish a valid methodology for an optimal manipulation and fixation of the brain tissue, which allows the samples to be viable for neuroanatomical and neuropathological studies. With this in view, we validated a methodology in order to preserve the quality of such large brains (neuroanatomy/neuropathology) and at the same time to obtain fresh brain samples for toxicological, virological, and microbiological analysis (neuropathology). A fixation protocol adapted to brains, of equal or even three times the size of human brains, was studied and tested. Finally, we investigated the usefulness of a panel of 20 antibodies (neuromarkers) associated with the normal structure and function of the brain, pathogens, age-related, and/or functional variations. The sampling protocol and some of the 20 neuromarkers have been thought to explore neurodegenerative diseases in these long-lived animals. To conclude, many of the typical measures used to evaluate neuropathological changes do not tell us if meaningful cellular changes have occurred. Having a wide panel of antibodies and histochemical techniques available allows for delving into the specific behavior of the neuronal population of the brain nuclei and to get a "fingerprint" of their real status.

Pulmonary and Systemic Skeletal Muscle Embolism in a Beaked Whale with a Massive Trauma of Unknown Aetiology.

An adult female Sowerby's beaked whale was found floating dead in Hermigua (La Gomera, Canary Islands, Spain) on 7 December 2016. Severe traumas of unknown aetiology were attributed, and the gross and microscopic findings are consistent with catastrophic trauma as a cause of death. Rib fractures affected the intercostals, transverse thoracis skeletal muscles, and thoracic rete mirabile. Degenerated muscle fibres were extruded to flow into vascular and lymphatic vessels travelling to several anatomic locations into the thoracic cavity, including the lungs, where they occluded the small lumen of pulmonary microvasculature. A pulmonary and systemic skeletal muscle embolism was diagnosed, constituting the first description of this kind of embolism in an animal. The only previous description has been reported in a woman after peritoneal dialysis. Skeletal pulmonary embolism should be considered a valuable diagnostic for different types of trauma in vivo in wild animals. This is especially valuable when working with decomposed carcasses, as in those cases, it is not always feasible to assess other traumatic evidence.

Aplicación Intralesional de Antimoniales en el Tratamiento de Leishmaniasis Cutánea

Resumen Objetivo: evaluar la eficacia clínica de la aplicación intralesional de 3 versus, 6 inyecciones de Glucantime®, durante una o dos semanas en pacientes con leishmaniasis cutánea. Métodos: estudio de tipo cuasi experimental. Se incluyó a 41 pacientes con leishmaniasis cutánea del área endémica tropical de Cochabamba, Bolivia. Los pacientes, fueron distribuidos aleatoriamente para recibir tratamiento intralesional con Glucantime®, en tres o seis aplicaciones. Todos ellos firmaron un consentimiento escrito de aceptación voluntaria de participar del estudio, que cuenta con el aval del comité de ética de la facultad de medicina UMSS. Resultados: la evaluación realizada a la eficacia clínica, del empleo de tres o seis aplicaciones intralesionales de Glucantime® no encontró diferencias estadísticamente significativas entre ambas. Así mismo, tampoco se encontró diferencias significativas en cuanto a la cicatrización completa alcanzada al primer mes post tratamiento por ambos esquemas de aplicación. Conclusiones: la cicatrización de las úlceras observada en este estudio, se consiguió independiente del esquema de tres o seis aplicaciones intralesionales de Glucantime® y estos resultados son comparables al tratamiento sistémico. Se considera que tres aplicaciones de Glucantime® intralesional es el límite mínimo como tratamiento para leishmaniasis cutánea con una sola úlcera cuyo tamaño sea menor a tres por tres centímetros.

Abstract Objective: to evaluate the clinical efficacy of intralesional application of 3 versus 6 injections of Glucantime® for one or two weeks in patients with cutaneous leishmaniasis. Methods: quasi-experimental study. 41 patients with cutaneous leishmaniasis were included from the tropical endemic area of Cochabamba, Bolivia. Participants were randomly assigned to receive intralesional treatment with Glucantime®, in three or six applications. All patients signed a written consent to voluntarily participate in the study, approved by the ethics committee of the UMSS medical school. Results: evaluation of the clinical effectiveness of three or six intralesional applications of Glucantime® found no statistically significant differences between the two. Likewise, no significance differences were found regarding complete healing achieved at one month post-treatment by both application schemes. Conclusions: ulcer healing observed in this study was achieved independent of the scheme of either three or six intralesional applications of Glucantime® and these results are comparable to systemic treatment. Three intralesional Glucantime® applications are considered to be the minimal treatment limit for cutaneous leishmaniasis with a single ulcer smaller than three by three centimeters.

A Study on the Pathological Effects of Trypanorhyncha Cestodes in Dusky Groupers Epinephelus marginatus from the Canary Islands.

Trypanorhyncha are cestodes commonly infecting marine fish. Numerous studies have detailed the biology of Trypanorhyncha species, but information on the pathological changes produced by these parasites is limited. Dusky groupers are keystone species necessary for the preservation of several marine ecosystems. Considering their vulnerable state of conservation and the efforts being made to culture them, identification of the effects caused by Trypanorhyncha is vital. Here, we aimed to determine the prevalence and pathological changes produced by Trypanorhyncha in dusky groupers from the Canary Islands. The prevalence of trypanorhynch plerocerci was 96%. Grossly, in the abdominal cavity, there were numerous larvae-filled cysts and nodules. These were embedded in abundant fibrosis, producing visceral adhesions. Histologically, affecting the peritoneum, stomach, and intestine there were numerous degenerated encysted plerocerci and extensive deposition of mature connective tissue. These findings indicate that Trypanorhyncha is highly prevalent in adult dusky groupers from the Canary Islands, producing a progressive and chronic response. Furthermore, fish immune system appears to attempt to eliminate the parasites through fibrous encapsulation. Nonetheless, extensive fibrosis may have a detrimental impact on fish health when adjacent cells or tissues are compressed and their functions impaired.

Myoglobin Concentration and Oxygen Stores in Different Functional Muscle Groups from Three Small Cetacean Species.

Compared with terrestrial mammals, marine mammals possess increased muscle myoglobin concentrations (Mb concentration, g Mb · 100g-1 muscle), enhancing their onboard oxygen (O2) stores and their aerobic dive limit. Although myoglobin is not homogeneously distributed, cetacean muscle O2 stores have been often determined by measuring Mb concentration from a single muscle sample (longissimus dorsi) and multiplying that value by the animal's locomotor muscle or total muscle mass. This study serves to determine the accuracy of previous cetacean muscle O2 stores calculations. For that, body muscles from three delphinid species: Delphinus delphis, Stenella coeruleoalba, and Stenella frontalis, were dissected and weighed. Mb concentration was calculated from six muscles/muscle groups (epaxial, hypaxial and rectus abdominis; mastohumeralis; sternohyoideus; and dorsal scalenus), each representative of different functional groups (locomotion powering swimming, pectoral fin movement, feeding and respiration, respectively). Results demonstrated that the Mb concentration was heterogeneously distributed, being significantly higher in locomotor muscles. Locomotor muscles were the major contributors to total muscle O2 stores (mean 92.8%) due to their high Mb concentration and large muscle masses. Compared to this method, previous studies assuming homogenous Mb concentration distribution likely underestimated total muscle O2 stores by 10% when only considering locomotor muscles and overestimated them by 13% when total muscle mass was considered.

Microscopic anatomical, immunohistochemical, and morphometric characterization of the terminal airways of the lung in cetaceans.

The lungs of cetaceans undergo anatomical and physiological adaptations that facilitate extended breath-holding during dives. Here, we present new insights on the ontogeny of the microscopic anatomy of the terminal portion of the airways of the lungs in five cetacean species: the fin whale (Balaenoptera physalus); the sperm whale (Physeter macrocephalus), the Cuvier's beaked whale (Ziphius cavirostris); the bottlenose dolphin (Tursiops truncatus); and the striped dolphin (Stenella coeruleoalba). We (a) studied the histology of the terminal portion of the airways; (b) used immunohistochemistry (IHC) to characterize the muscle fibers with antibodies against smooth muscle (sm-) actin, sm-myosin, and desmin; (c) the innervation of myoelastic sphincters (MESs) with an antibody against neurofilament protein; and (d) defined the diameter of the terminal bronchioles, the diameter and length of the alveoli, the thickness of the septa, the major and minor axis, perimeter and section area of the cartilaginous rings by quantitative morphometric analyses in partially inflated lung tissue. As already reported in the literature, in bottlenose and striped dolphins, a system of MESs was observed in the terminal bronchioles. Immunohistochemistry confirmed the presence of smooth muscle in the terminal bronchioles, alveolar ducts, and alveolar septa in all the examined species. Some neurofilaments were observed close to the MESs in both bottlenose and striped dolphins. In fin, sperm, and Cuvier's beaked whales, we noted a layer of longitudinal smooth muscle going from the terminal bronchioles to the alveolar sacs. The morphometric analysis allowed to quantify the structural differences among cetacean species by ranking them into groups according to the adjusted mean values of the morphometric parameters measured. Our results contribute to the current understanding of the anatomy of the terminal airways of the cetacean lung and the role of the smooth muscle in the alveolar collapse reflex, crucial for prolonged breath-holding diving.

Sistema Inmune, Infección por SARS-CoV-2 y Desarrollo de COVID-19

Resumen La infección por SARS-CoV-2 promueve un descontrol del sistema inmune con predominio de una respuesta inflamatoria de rápida instauración y el desencadenamiento de una tormenta de citocinas. El objetivo de esta revisión es comprender mejor los mecanismos inmunológicos y su descontrol activados por SARS-CoV-2. La activación de la inmunidad innata, contra la infección, es el factor clave para el control viral o su progresión hacia COVID-19. La respuesta inmune adaptativa, igualmente es perturbada por SARS-CoV-2 con lo cual se posibilita una mayor tasa de infección, así como también el descontrol inmunológico sistémico que puede desencadenar shock y daño tisular en diferentes órganos, muerte por COVID-19 o autoinmunidad post COVID-19.

Abstract The SARS-CoV-2 infection promotes a lack of control of the immune system with a predominance of a rapidly onset inflammatory response and the triggering of a cytokine storm. The objective of this review is to understand better the immune mechanisms and their lack of control activated by SARS-CoV-2. The activation of innate immunity against infection is the key factor for viral control or its progression towards COVID-19. The adaptive immune response is also disturbed by SARS-CoV-2, which enables a higher infection rate, as well as systemic immune lack of control that can trigger shock and tissue damage in different organs, death from COVID-19 or autoimmunity post-COVID-19.

Tratamiento Combinado en Leishmaniasis Cutánea con Falla Terapéutica

Resumen La leishmaniasis tegumentaria en Bolivia es producida mayoritariamente por L. braziliensis. Las manifestaciones clínicas son ulceras, que pueden generar lesiones satélites próximas a la inicial. Las drogas de primera elección para el tratamiento son los antimoniales pentavalentes; aunque con una eficacia variable. La falta de respuesta a estas drogas, induce al empleo de otras, consideradas como de segunda elección. Sin embargo, en todos los casos existe la posibilidad de falla terapéutica. El presente caso muestra la remisión de las lesiones usando tratamiento combinado de pentamidina, miltefosina y paromomicina, en un paciente con antecedente de falta de respuesta a la monoterapia con Glucantime®. La remisión de la enfermedad alcanzada al final de la terapia, probablemente sea resultado de la acción lítica simultánea de las tres drogas utilizadas y a la restauración de la respuesta inmune del paciente. Hasta los 21 meses de control pos tratamiento, todas las lesiones se mantuvieron cicatrizadas y ausencia de otras nuevas.

Abstract The tegumentary leishmaniasis in Bolivia is mainly caused by L. braziliensis. The clinical manifestations are ulcerative lesions which can generate satellite lesions close to the initial one. The first choice drugs for treatment are pentavalent antimonials; although with variable effectiveness. Lack of response to these drugs leads to the use of other alternatives, considered as second-choice drugs. However, in all cases there is the possibility of therapeutic failure. The present case shows the remission of the lesions using a combined treatment of pentamidine, miltefosine and paromomycin, in a patient with a history of lack of response to monotherapy with Glucantime® The remission of the disease achieved at the end of combined therapy is probably the result of the simultaneous lytic action of the three drugs used and the restoration of the patient's immune response. Up to 21 months of post-treatment control, all the lesions remained healed and the absence of new ones.

Retrospective Study of Fishery Interactions in Stranded Cetaceans, Canary Islands.

Estimating cetacean interactions with fishery activities is challenging. Bycatch and chronic entanglements are responsible for thousands of cetacean deaths per year globally. This study represents the first systematic approach to the postmortem investigation of fishery interactions in stranded cetaceans in the Canary Islands. We retrospectively studied 586 cases necropsied between January 2000 and December 2018. Of the cases with a known cause of death, 7.4% (32/453) were due to fishery interactions, and the Atlantic spotted dolphin (Stenella frontalis) was the most affected species [46.9% (15/32)]. Three types of fishery interactions were recognized by gross findings: bycatch [65.6% (21/32)], chronic entanglements [18.8% (6/32)], and fishermen aggression [15.6% (5/32)]. Among the bycaught cases, we differentiated the dolphins that died because of ingestion of longline hooks [23.8% (5/21)] from those that died because of fishing net entrapments [76.2% (16/21)], including dolphins that presumably died at depth due to peracute underwater entrapment (PUE) [37.5% (6/16)], dolphins that were hauled out alive and suffered additional trauma during handling [43.8% (7/16)], and those that were released alive but became stranded and died because of fishery interactions [18.7% (3/16)]. Gross and histologic findings of animals in each group were presented and compared. The histological approach confirmed gross lesions and excluded other possible causes of death. Cetaceans in good-fair body condition and shallow diving species were significantly more affected by fishery interactions, in agreement with the literature. Low rates of fishery interactions have been described, compared with other regions. However, within the last few years, sightings of entangled live whales, especially the minke whale (Balaenoptera acutorostrata) and Bryde's whale (B. edeni), have increased. This study contributes to further improvement of the evaluation of different types of fishery interactions and may facilitate the enforcement of future conservation policies to preserve cetacean populations in the Canary Islands.

Retrospective Study of Traumatic Intra-Interspecific Interactions in Stranded Cetaceans, Canary Islands.

Aggressive encounters involving cetacean species are widely described in the literature. However, detailed pathological studies regarding lesions produced by these encounters are scarce. From January 2000 to December 2017, 540 cetaceans stranded and were necropsied in the Canary Islands, Spain. Of them, 24 cases of eight species presented social traumatic lesions produced by cetaceans of the same or different species. All the cases presented severe multifocal vascular changes, 50% (12/24) presented fractures affecting mainly the thoracic region, 41.7% (10/24) acute tooth-rake marks, 37.5% (9/24) undigested food in the stomach, 33.3% (8/24) tracheal edema, and 12.5% (3/24) pulmonary perforation. In 10 cases with tooth-rake marks, the distance between the teeth, allowed us to further identify the aggressor species: four cases were compatible with killer whales (Orcinus orca) affecting three species [pigmy sperm whale (Kogia breviceps), Cuvier's beaked whale (Ziphius cavirostris), and short-finned pilot whale (Globicephala macrorhynchus)] and four cases compatible with common bottlenose dolphins (Tursiops truncatus) affecting two species [short-beaked common dolphin (Delphinus delphis) and Atlantic spotted dolphin (Stenella frontalis)]. We also described two cases of intraspecific interaction in stripped dolphin (Stenella coeruleoalba). Microscopically, 70.8% (17/24) of the cases presented acute degenerative myonecrosis, 66.7% (14/21) presented vacuoles in the myocardiocytes, 36.8% (7/19) pigmentary tubulonephrosis, 31.6% (6/19) cytoplasmic eosinophilic globules within hepatocytes, 21.4% (3/14) hemorrhages in the adrenal gland, and 17.3% (4/23) bronchiolar sphincter contraction. The statistical analysis revealed that deep divers, in good body condition and nearby La Gomera and Tenerife were more prone to these fatal interactions. Additionally, in this period, three animals died due to an accident during predation: a false killer whale (Pseudorca crassidens) died because of a fatal attempt of predation on a stingray, and two Risso's dolphins (Grampus griseus) died as a consequence of struggling while predating on large squids.

Morphological structure of the aortic wall in three Delphinid species with shallow or intermediate diving habits: Evidence for diving adaptation.

Some modifications in the vascular system of marine mammals provide adaptive advantages for diving. This study analyses the organisation of the aortic wall in dolphins, observing artery changes in volume and blood pressure for diving behaviour. Samples of three aortic segments (ascending, thoracic and abdominal) of three dolphin species were processed for histological and morphometric studies. The three dolphin species used, striped dolphin (Stenella coeruleoalba), Atlantic spotted dolphin (Stenella frontalis) and common dolphin (Delphinus delphis), have shallow or intermediate diving habits. Our results indicated that the components of the aortic wall of the dolphins had different dispositions in the three selected segments. The aortic wall decreased in thickness along its length due to a loss of the lamellar units in the tunica media and a thinning of the main elements of the lamellar units along the artery. The life stage had little influence on the thickness of the aortic wall except for the ascending aorta. The weight, body length, species or sex of the specimen did not significantly influence the thickness of the wall or the lamellar units. In summary, the histological and morphometric aortic structure in dolphins, in relation to the studied parameters, seems to be similar to that previously described of terrestrial mammals such as pigs, except for a larger difference in the proportion of lamellar units between the ascending and thoracic segments.