Sternal foramina and variant xiphoid morphology in a Kenyan population.

Sternal foramina may pose a great hazard during sternal puncture, due to inadvertent cardiac or great vessel injury. They can also be misinterpreted as osteolytic lesions in cross-sectional imaging of the sternum. On the other hand, variant xiphoid morphology such as bifid, duplicated, or trifurcated may be mistaken for fractures during imaging. The distribution of these anomalies differs between populations, but data from Africans is scarcely reported. This study therefore aimed to investigate the distribution and frequency of sternal foramina and variant xiphoid morphology in a Kenyan population. Eighty formalin-fixed adult sterna (42 males [M], 38 females [F]) of age range 18-45 years were studied during dissection at the Department of Human Anatomy, University of Nairobi. Soft tissues were removed from the macerated sterna by blunt dissection and foramina recorded in the manubrium, body, and xiphoid process. The xiphisternal ending was classified as single, bifurcated (2 xiphoid processes with a common stem), or duplicated (2 xiphoid processes with separate stems). Results were analysed using SPSS version 17.0. Foramina were present in 11 specimens (13.8%): 7 M, 4 F. The highest frequency was in the sternal body (n = 9), where they predominantly occurred at the 5th intercostal segment. Xiphoid foramina were present in 2 specimens (both males) (2.5%), while manubrial foramen was not encountered. The xiphisternum ended as a single process in 64 cases (34 M, 30 F) (80%). It bifurcated in 10 cases (5 M, 5 F) (12.5%), and duplicated in 6 cases (4 M, 2 F) (7.5%). There were no cases of trifurcation. Sternal foramina in Kenyans vary in distribution and show higher frequency than in other populations. These variations may complicate sternal puncture, and due caution is recommended. The variant xiphisternal morphology may raise alarm for xiphoid fractures and may therefore be considered a differential.

Variant origin of the lateral circumflex femoral artery in a black Kenyan population.

Variant origin of lateral circumflex femoral artery (FA) is important during harvesting of anterolateral thigh flaps, aortopopliteal by-pass, coronary artery grafting, and vascularised iliac transplant. The frequencies of variant origins display ethnic variations, but reports from black Africans are scarce. This study, therefore, aimed to describe the variant origins of lateral circumflex FA in a black Kenyan population. Eighty-four (42 right and 42 left) lateral femoral circumflex arteries from 42 cadavers (31 male and 11 female) were exposed by dissection of the femoral triangles at the Department of Human Anatomy, University of Nairobi. The arteries were then traced proximally to their parent trunks. Sites of origin were recorded and representative images of the variations taken using a high-resolution digital camera. Data were analysed using Statistical Program for Social Scientists version 16.0 for Windows and presented in tables and macrographs. The lateral circumflex artery was a branch of the profunda femoris in only 65.5% of cases. Variant origins included from a common trunk with medial circumflex artery (14.3%), with profunda femoris (10.7%), as a trifurcation with profunda femoris and medial circumflex FA (7.1%), and from FA (2.4%). Variant origin of the lateral circumflex FA occurred in nearly 35% of the Kenyan population studied, much lower than in oriental populations. The most frequent variant origin is as a common trunk with medial circumflex femoral and profunda femoris, with a very low prevalence of origin from FA. The unusual origins make the artery more vulnerable to iatrogenic injury during surgery and catheterisation. Preoperative angiographic evaluation of the femoral arterial system is recommended.

Sex variations in the structure of human atrioventricular annuli.

Atrioventricular annuli are important in haemodynamic flexibility, competence, and support for tricuspid and mitral valves. The anatomical features of the annuli, such as circumference, organisation of connective tissue fibres, myocardium, and cellularity, may predispose to annular insufficiency and valvular incompetence. These pathologies occur more commonly in females, although the anatomical basis for this disparity is unclear. Sex variation in the structure of the annuli is important in providing a morphological basis for the patterns of these diseases. This study therefore aimed to determine the sex variations in the structure of human atrioventricular annuli. One hundred and one hearts (48 males, 53 females) obtained from the Department of Human Anatomy of the University of Nairobi were studied. Annular circumferences were measured using a flexible ruler and corrected for heart weight. Results were analysed using SPSS version 17.0 and sex differences determined using student's t-test. A p-value of less than 0.05 was considered significant. For light microscopy, specimens were harvested within 48 hours post-mortem, processed, sectioned, and stained with Masson's trichrome and Weigert's elastic stain with van Gieson counterstaining. Females had significantly larger annular circumferences than males after correcting for heart weight (p ≤ 0.05). Histologically, myocardium was consistently present in all male annuli while this was absent in females except in one specimen. The annuli were more elastic and cellular in males especially in the annulo-myocardial and annulo-valvular zones, respectively. The corrected larger annular circumference in females may limit heart valve coaptation during cardiac cycle and may be a risk factor for valvular insufficiency. The predominance of myocardium, annular cellularity, and elasticity may be more protective against heart valve incompetence in males than in females.

Variant anatomy of sciatic nerve in a black Kenyan population.

Knowledge of variant anatomy of the sciatic nerve is important in avoiding inadvertent injury during operations in the gluteal region and interpreting nondiscogenic sciatica. This variant anatomy may cause piriformis syndrome and failure of sciatic nerve block. The variations differ between populations but data from Africans is scarce. This study, therefore, investigated variations of sciatic nerve in a black Kenyan population. One hundred and sixty-four sciatic nerves from 82 cadavers of black Kenyans were exposed by dissection at the Department of Human Anatomy, University of Nairobi, Kenya. The level of bifurcation, relationship to piriformis, and topographic relations between the branches were studied. The results were analysed by SPSS version 16.0 and are presented by macrographs. In 33 (20.1%) cases division occurred in the pelvis, while in 131 (79.9%) it occurred outside the pelvis. A single trunk sciatic nerve exited below the piriformis muscle in 131 (79.9%) cases. In cases of pelvic division, the tibial nerve was always infrapiriformic, while the common peroneal nerve passed below piriformis in 16 (9.8%) cases, pierced the piriformis in 13 (7.9%), and passed above it in 4 (2.4%). For those in which division was extrapelvic, 110 (67.1%) were in the popliteal fossa, 17 (10.4%) in the middle third of the thigh, and 4 (2.4%) in the gluteal region. Where the division was pelvic, in 19 (11.6%) cases they continued separately, in 8 (4.9%) the two nerves reunited, and in 6 (3.7%) they were connected by a communicating nerve. The sciatic nerve in the Kenyan population varies from the classical description in over 30% of cases, with many high divisions, low incidence of piriformic course of common peroneal nerve, reunion, and unusual connection between common peroneal and tibial nerves. These variations may complicate surgery and interpretation of sciatic neuropathy. Preoperative nerve imaging and extra operative diligence in the gluteal region and the back of the thigh are recommended.

Variations in the anatomy of ansa cervicalis.

With the emerging utilisation of ansa cervicalis in nerve reconstructive surgery, it is important for surgeons to be conversant with the anatomy of these nerves. This descriptive cross sectional study aimed at describing the morphology and topographic anatomy of ansa cervicalis. We examined 38 adult human formalin-fixed cadavers. The superior root was present in 38 (100%) cases and 37 (97%) cases, on the right and left sides, respectively. More than half (56%) of these roots were located superior to the posterior belly of the digastric muscle. The inferior root, on the other hand, was present in 34 (89.5%) cases on the right side and 31 (81.6%) cases on the left side. Of all the inferior roots, 81.5% were located lateral to the internal jugular vein. The loop was seen in all the cases that had the inferior root, and was mostly (64.6%) located above the superior belly of the omohyoid muscle. Knowledge of the anatomy of ansa cervicalis is not only important for nerve reconstruction surgeries, but also for operations in the neck, so as to avoid injuring the great vessels that are closely related to it.

Structural organisation of tunica intima in the aorta of the goat.

The structural organisation of tunica intima in the aorta is important for its integrity, prediction, and diagnosis of atherosclerosis. The goat is a suitable model for cardiovascular studies, but the structure of its tunica intima is scarcely reported. This study, therefore, aimed to describe features of the goat aortic tunica intima by light and transmission electron microscopy. Sixteen healthy male domestic goats (capra hircus) aged between 6 and 24 months were used: 8 for light and 8 for electron microscopy. The animals were euthanised with sodium pentabarbitone 20 mg/mL and fixed with 3% phosphate buffered glutaraldehyde. For light microscopy, specimens from various regions of the aorta were routinely processed for paraffin embedding and 7 mm sections stained with Mason's trichrome. Those for transmission electron microscopy were post fixed in osmium tetroxide, embedded in Durcupan, and ultrathin sections stained with uranyl acetate and counter stained with lead citrate. Endothelium comprises round and squamous cells, linked to the subendothelial material by a simple and sometimes lamellated basement membrane. In the subendothelial zone, a heterogenous population of cells are connected with interlinked collagen and elastic fibres. Both cells and fibres are connected to the internal elastic lamina. The composite structure and interlinkages in the tunica intima permit unitary function and increase mechanical strength, thus enabling it to withstand haemodynamic stress.

The suprascapular notch: its morphology and distance from the glenoid cavity in a Kenyan population.

The morphology of the suprascapular notch has been associated with suprascapular entrapment neuropathy, as well as injury to the suprascapular nerve in arthroscopic shoulder procedures. This study aimed to describe the morphology and morphometry of the suprascapular notch. The suprascapular notch in 138 scapulae was classified into six types based on the description by Rengachary. The suprascapular notch was present in 135 (97.8%) scapulae. Type III notch, a symmetrical U shaped notch with nearly parallel lateral margins, was the most prevalent type, appearing in 40 (29%) scapulae. The mean distance from the notch to the supraglenoid tubercle was 28.7 ± 3.8 mm. This varied with the type of notch, being longest in type IV (30.1 ± 1.8 mm) and shortest in type III (27.3 ± 2.3 mm). The mean distance between the posterior rim of the glenoid cavity and the medial wall of the spinoglenoid notch at the base of the scapular spine was found to be 15.8 ± 2.2 mm. Type III notch was the most prevalent, as found in other populations. In a significant number of cases the defined safe zone may not be adequate to eliminate the risk of nerve injury during arthroscopic shoulder procedures, even more so with type I and II notches.

Regional differences in aorta of goat (capra hircus).

Regional differences in the aortic wall are important in explaining the physicomechanical properties and disease distribution in this artery. The goat is a suitable model for studying cardiovascular disease, but the regional features of its aorta are scarcely reported. The purpose of the study was therefore to describe the regional differences in the wall of its aorta. Sixteen healthy adult male domestic goats (capra hircus) were euthanised with intravenous sodium pentabarbitone and specimens obtained from the ascending, arch, each vertebral level of descending thoracic, and various segments of abdominal aorta. The specimens were fixed in 10% formaldehyde solution and routinely processed for paraffin embedding. Seven micron thick sections were stained with Mason's Trichrome and Weigert Resorcin Fuchsin stains. Light microscopic examination revealed that the aortic wall consists of tunica intima comprising endothelium, subendothelial zone and internal elastic lamina, media, and adventitia. Endothelium comprises flat and round endotheliocytes. The population of round cells declines as the internal elastic lamina increases in prominence caudally. Tunica media in ascending, arch, and proximal thoracic aorta comprises two zones: namely a luminal elastic and adventitial musculo-elastic zone, in which muscle islands interrupt some elastic lamellae. These islands progressively diminish caudally until by the eleventh thoracic vertebra they are only patchy. Beyond this point and in the abdominal aorta they are absent and tunica media consists of regular concentric elastic lamellae. Tunica adventitia, on the other hand, increases in thickness and elastic fibre content caudally. Regional variations exist in all three layers of goat aorta. The nature of these differences suggests that they are related to haemodynamic factors. Furthermore, the variations may form the basis for regional differences in physicomechanical strength and disease distribution along the aorta.

Morphometry and variations of bony ponticles of the atlas vertebrae (C1) in kenyans / Morfometría y variaciones de puentes óseos de la vértebra atlas (C1) en kenianos

Atlas bridges, the bony outgrowths over the third segment of the vertebral artery are associated with compression of the artery and nerves. There are limited studies comparing morphometry of the complete atlas bridges and that of the ipsilateral transverse foramen. Bilateral and gender differences in the morphometry of the complete bridges remain relatively unexplored. One hundred and two atlas vertebrae (49 male and 53 female) obtained from the Osteology Department of the National Museums of Kenya were used for this study. The presence of complete posterior atlas bridge (retroarticular canal) and lateral bridge (supratransverse foramen) was noted. Measurements were taken for the diameters of foramina, and the ipsilateral transverse foramina and their areas calculated. Complete posterior bridges occurred in 14.6 percent and 13.6 percent on the right and left sides respectively. The lateral bridge was found in 3.9 percent of the cases on the right side only. The complete posterior bridges had a cross-sectional area of 23.44mm2 on the right and 24.98mm2 on the left side. The lateral bridges had a mean cross-sectional area of 27.30mm2. The right and left transverse foramina had mean crosssectional area of 36.30mm2 and 37.20mm2 respectively, which was significantly larger than that of the ipsilateral complete and posterior bridges. The smaller dimensions of the complete atlas bridges compared to the ipsilateral transverse foramen suggest that they may predispose to vertebrobasilar insufficiency, Barre-Lieou and cervicogenic syndromes due to compression of the contents in the foramina.

Puentes del atlas, sobrecrecimientos óseos en el tercer segmento de la arteria vertebral se asocian con la compresión de la arteria y los nervios. Hay pocos estudios que comparan la morfometría de los puentes completos del atlas y el foramen transversal ipsilateral. Diferencias bilaterales y de género en la morfometría de los puentes completos permanecen relativamente inexplorados. Ciento dos vértebras atlas (49 hombres y 53 mujeres) obtenidos del Departamento de Osteología de los Museos Nacionales de Kenya se utilizaron para este estudio. Fueron identificados la presencia de puentes completos posteriores del atlas (canal retroarticular) y puentes laterales (foramen supratransverso). Se realizaron las mediciones de los diámetros del foramen y los forámenes transversos ipsilaterales, y se calcularon sus áreas. Puentes completos posteriores se observaron en el 14,6 por ciento y 13,6 por ciento de los lados derecho e izquierdo, respectivamente. El puente lateral se encontró en el 3,9 por ciento de los casos en el lado derecho solamente. Los puentes completos posteriores tuvieron un área transversal de 23,44mm2 en el lado derecho y 24,98mm2 en el lado izquierdo. Los puentes laterales tuvieron un área media de sección transversal de 27,30mm2. En los lados derecho e izquierdo se encontrron forámenes transversos con un área promedio de sección transversal de 36,30mm2 y 37,20mm2 respectivamente, lo que fue significativamente mayor que el de los puentes completos ipsilaterales y posteriores. Las dimensiones más pequeñas de los puentes atlas completos en comparación con los forámenes transversos ipsilaterales sugieren que pueden predisponer a la insuficiencia vertebrobasilar, síndromes de Barre-Lieou y cervical debido a la compresión de los contenidos en los forámenes.

Superficial temporal artery among Kenyans: pattern of branching and its relation to pericranial structures.

The superficial temporal artery, one of the terminal branches of the external carotid artery, is used for temporoparietal, parieto-occipital flaps and forehead flaps in reconstructive surgery. The topographic anatomy of this artery exhibits ethnic variations. Therefore, this study aimed to determine the branching pattern of the superficial temporal artery and its relation to specified landmarks in the pericranial region among Kenyans. Sixty superficial temporal arteries from thirty adult cadavers (18 male, 12 female), obtained from the Department of Human Anatomy, were examined during dissection. The number of branches and pattern of branching of the superficial temporal artery was recorded. Specific measurements were taken from the branching point to the lateral canthus, tragus, and midpoint of the arch of the zygoma. Classical bifurcation into a parietal and a frontal branch was seen in 16 (53.3%) cases. Double frontal and double parietal branches were reported in 26.7% and 13.3% of cases, respectively. Only two cases had a trifurcation. The point of origin of the branches in most cases (80%) was above the arch of the zygoma. The mean distance to the midpoint of the arch of the zygoma was 50.8 + or - 20.9 mm, to the lateral canthus 58.6 + or - 24.3 mm, and to the tragus 44.1 + or - 18.5 mm. The branching pattern among Kenyans, therefore, differs from the classical descriptions. A good understanding of the forehead vascularity aids in the design of flaps and minimizes postoperative complications.

Spinal cord termination in adult Africans: relationship with intercristal line and the transumbilical plane.

The level of cord termination and level of vertebral intersection of intercristal line and transumbilical plane (TUP), frequently used landmarks, show ethnic variation. The relationship of the spinal cord termination to these lines is vital in spinal surgery and anesthesia, but data on these parameters are scarce in the African population. The purpose of this work is to determine the level of cord termination and establish its relationship with intercristal line and TUP. One hundred and twelve specimens obtained from the department of Human Anatomy at the University of Nairobi were used in this study. The conus medullaris was exposed by laminectomy and its vertebral level together with those of intercristal line and TUP recorded. The distance of conus medullaris from intercristal plane was measured in millimeters. Data obtained were coded and analyzed using Statistical Package for Social Sciences (SPSS) for windows version 16.0 Chicago, Illinois, 2002. Student's t-test was used in the statistical assessment of gender differences. A P value of less than 0.05 was considered significant. The median level of termination of the cord was the upper third of L2, 51.9% of cases terminating below this. There was no statistically significant gender difference in the level of termination of the cord. The intercristal plane passed through L4/L5 disc (70.9%) and below (29.1%). The TUP corresponded with intercristal line in 78.2% of subjects. The mean distance of the spinal cord termination from intercristal line was 99 +/- 24 mm. The spinal cord terminates at or below the upper third of L2. Care should be exercised during lumbar punctures and spinal epidural anesthesia among Africans. Intecristal line and TUP are safe landmarks to use in location of conus medullaris.

Morphology of human myocardial bridges and association with coronary artery disease.

BACKGROUND: The functional significance of myocardial bridging remains controversial. The bridge morphology and structure of the tunneled vessels may modify its ultimate clinical effects. OBJECTIVE: To describe the morphological characteristics of myocardial bridges and their influence on coronary histology. DESIGN: A descriptive cross-sectional study. METHODS: One hundred and nine formalin-fixed adult hearts were evaluated by dissection for these data: prevalence, site, lengths and depths of myocardial bridges. Vessel segments proximal and distal to the bridged portion were also processed for histology and stained to elaborate smooth muscle, collagen and elastic fibers. Stereology was also employed to compare the relative sizes of the tunica intima and the vessel wall to lumen ratios. RESULTS: Myocardial bridges were found in 40.4% of the hearts, most commonly in the left anterior descending artery (LAD). The average length of the bridges was 22.66 +11.94 mm while the depth was 1.83+ 0.98mm, with only 11% being long (34.87mm - 50mm) and 9% of them being deep (3.46mm - 5.00mm). The tunica intima was thickest proximal to and thinnest under the myocardial bridge. The intima of the proximal segment was also more elastic. An elaborate perivascular 'cushion' of adipose tissue intervened between the intramural coronary and the surrounding myocardium. CONCLUSIONS: Most myocardial bridges are superficial and short. Tunica intima under myocardial bridges is spared from "atherogenesis". The thick perivascular space around the bridged segment may protect it from extreme compression.

Regional histomorphometry of the hepatic inferior vena cava; a possible sphincteric mechanism / Histomorfometría regional de la vena cava inferior hepática; un posible mecanismo de esfínter

This study was aimed at identifying the changes in diameter and structural composition of the Hepatic Inferior Vena Cava in its infrahepatic, intrahepatic and suprahepatic portions. Eighty adult liver specimens from the Chiromo and Nairobi City mortuaries were used for morphometry, while twenty of them were processed for light microscopy. A constriction was noted in the mid-portion of the HIVC, while structurally; the intrahepatic portion had thicker fibromuscular adventitia. It is plausible that these are sphincteric apparatus to prevent backflow of blood in the Hepatic Inferior Vena Cava.

Este estudio tiene por objetivo identificar los cambios en el diámetro y la composición estructural de la vena cava inferior hepática en sus porciones infrahepática, intrahepática y suprahepática. Ochenta hígados de especímenes adultos de los depósitos de cadáveres de la ciudad de Nairobi y Chiromo fueron usadas para morfometría, mientras que veinte de ellos fueron procesados para microscopía de luz. Se observó una constricción en el medio de la HIVC, mientras que estructuralmente, la porción intrahepática había una gruesa adventicia fibromuscular. Es posible que este sea un aparato esfinteriano para evitar el reflujo de sangre en la vena cava inferior hepática.

Anatomical variations of the carotid arteries in adult Kenyans.

OBJECTIVE: To describe the topography and anatomical variations of the carotid arteries among Kenyans. DESIGN: A descriptive cross-sectional study. SETTING: Department of Human Anatomy, University of Nairobi. SUBJECTS: Eighty carotid arteries of forty cadavers were dissected. RESULTS: The bifurcation of the commonest carotid artery was high (above the reference points) in 63.8% of vessels and the external carotid was antero-lateral to the internal carotid artery in 30% of the vessels. A linguo-facial trunk was the most common variation of the external carotid artery. The origin of the right common carotid artery was high and low in 10% and 2.6% of vessels respectively. CONCLUSION: The carotid arteries show important variability and thus emphasise caution for clinicians during surgical procedures in the neck.

Biometric features of facial foramina in adult Kenyan skulls

Several studies have indicated ethnic, age andsex-related variations in the position and sizeof the facial foramina. The present studyreports the biometric features of the mentalforamen (MF), and infraorbital (IO), supraorbital(SO), and zygomaticofacial (ZF) foraminain a sample of adult Kenyan skulls. Onehundred and four adult human skulls wereevaluated for the sizes, positions, multiplicity,symmetry and geometries of the MF, IO, SO,and ZF foramina. Our observations reveal thatthe MF was present in all 104 sku1ls. The distanceof the mental foramina from the symphysismenti ranged from 16.5 mm to 34.0 mm.The IO foramina were multiple in 5% of theskulls. The IO foramen was positioned6.26±1.8 mm from the inferior orbital marginand 32.87±3 mm from the superior alveolarmargins, respectively. The distance from thesuperior alveolar process was greater in males.The distance of the MF, IO and SO from themidline was about 27 mm. ZF were absent in3-4% of the skulls and multiple in 50% of theskulls. Ten percent of the supraorbital passageswere foramina; 60% were notches, whilethe rest were both notches and foramina. Inconclusion, the biometric characteristics of thefacial foramina reveal variations in Kenyanskulls. Clinicians operating in this area shouldbe aware of this anatomy and dimorphic sexualfeatures when anaesthetizing and operatingin the facial region (AU)

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Prevalence and Distribution of the Third Coronary Artery in Kenyans / Prevalencia y Distribución de la Tercera Arteria Coronaria en Kenianos

A third coronary artery (TCA) has been defined as a direct branch from the right aortic sinus (RAS) that contributes to the vascularization of the infundibulum of the right ventricle (RV). The distribution of this artery may be important in surgical procedures and in understanding the extent and progression of acute myocardial infarction. Its reported prevalence however shows ethnic disparity. The aim of the study was describe the prevalence and distribution of the third coronary artery in a Kenyan population. 148 cadaveric and postmortem human adult hearts obtained from the Department of Human Anatomy, University of Nairobi, and the Chiromo and Nairobi city mortuaries were used after an ethical approval. The hearts were studied by gross dissection for the prevalence and topographical anatomy of the TCA. Data was coded and analyzed using SPSS. The TCA is present in 35.1% of the heart specimens. It was variably distributed to the conducting system (23%), anterior wall of the RV (100%), interventricular septum (IVS) (51.9%) and the apex of the heart (5.8%). The TCA, with substantial contribution to cardiac vascularization, may be present in about a third of the Kenyans. It may constitute a significant collateral circulation to apical and septal perfusión. Interpretation of signs and symptoms of coronary occlusion should therefore consider possible contribution of this vascular channel.

La tercera arteria coronaria (TCA) ha sido definida como una rama directa del seno aórtico derecho (RAS) y contribuye a la vascularización del cono arterioso del ventrículo derecho (RV). La distribución de esta arteria puede ser importante en los procedimientos quirúrgicos y para comprender la magnitud y progresión del infarto agudo del miocardio. El reporte de su prevalencia, sin embargo, muestra disparidad étnica. Se describen la prevalencia y distribución de la tercera arteria coronaria en la población keniana, en un estudio transversal. Se utilizaron 148 corazones de cadáveres adultos, obtenidos del Departamento de Anatomía de la Universidad de Nairobi y de las morgues, de las ciudades de Chiromo y Nairobi, luego de su aprobación ética. Se estudiaron en los corazones por medio de la disección macroscópica, la anatomía topográfica de la TCA y su prevalencia. Los datos fueron codificados y analizados utilizando el software SPSS. La TCA estuvo presente en el 35,1% de los corazones. Su distribución variable fue del 23% en el sistema de conducción cardíaco, un 100% en la pared anterior del ventrículo derecho, 51,9% en el septo interventricular (IVS) y en el ápex del corazón un 5,8%. La tercera arteria coronaria contribuye sustancialmente a la vascularización cardiaca y puede estar presente en cerca de un tercio de los kenianos. Esto puede constituir una significativa circulación colateral para la perfusiones apical y septal. En la interpretación de signos y síntomas de oclusión coronaria se puede considerar la posible contribución de este vaso.

Evaluation of risk factors for Alzheimer's disease in elderly east Africans.

A number of biological risk factors have been implicated for Alzheimer's disease (AD). The investigation of prevalence rates of AD in crosscultural populations has much potential in validating these factors. We previously assessed brain amyloid beta (A beta) protein deposition and other lesions associated with AD as possible markers for preclinical AD in elderly nondemented East Africans. In further analysis, we demonstrate that 17-19% of elderly East African subjects without clinical neurological disease exhibited neocortical A beta deposits and minimal neurofibrillary changes at necropsy that was qualitatively and quantitatively similar to that in an age-matched elderly control sample from Cleveland, OH. A beta deposits varied from numerous diffuse to highly localized neuritic plaques and were predominantly reactive for the longer A beta 42 species. In parallel studies, we evaluated another recently implicated factor in AD, the apolipoprotein E genotype. We found relatively high frequencies of the apolipoprotein E-epsilon 4 allele in elderly nondemented East Africans. The frequencies were comparable to those in other African populations but higher than in subjects from developed countries. Our limited study suggests that elderly East Africans acquire cerebral lesions found in AD subjects but the apolipoprotein E-epsilon 4 allele may not be a highly specific factor for the disease among East Africans.

Cerebral amyloid beta protein deposits and other Alzheimer lesions in non-demented elderly east Africans.

There is little knowledge of the existence of Alzheimer disease (AD) or Alzheimer type of dementia in indigenous populations of developing countries. In an effort to evaluate this, we assessed the deposition of amyloid beta (A beta) protein and other lesions associated with AD in brains of elderly East Africans. Brain tissues were examined from 32 subjects, aged 45 to 83 years with no apparent neurological disease, who came to autopsy at two medical Institutions in Nairobi and Dar es Salaam. An age-matched sample from subjects who had died from similar causes in Cleveland was assessed in parallel. Of the 20 samples from Nairobi, 3 (15%) brains exhibited neocortical A beta deposits that varied from numerous diffuse to highly localized compact or neuritic plaques, many of which were also thioflavin S positive. Two of the cases had profound A beta deposition in the prefrontal and temporal cortices and one of these also exhibited moderate to severe cerebral amyloid angiopathy. Similarly, 2 of the 12 samples from Dar es Salaam exhibited diffuse and compact A beta deposits that were also predominantly reactive for the longer A beta 42 species compared to A beta 40. We also noted that A beta plaques were variably immunoreactive for amyloid associated proteins, apolipoprotein E, serum amyloid P and complement C3. Tau protein reactive neurofibrillary tangles (NFT) were also evident in the hippocampus of 4 subjects. By comparison, 4 (20%) of the 20 samples from randomly selected autopsies performed in Cleveland showed A beta deposits within diffuse and compact parenchymal plaques and the vasculature. These observations suggest A beta deposition and some NFT in brains of non-demented East Africans are qualitatively and quantitatively similar to that in age-matched elderly controls from Cleveland. While our small scale study does not document similar prevalence rates of preclinical AD, it suggests that elderly East Africans are unlikely to escape AD as it is known in developed countries.

Structure and sympathetic innervation of the intracranial arteries in the giraffe (Giraffa camelopardalis).

Fluorescence histochemistry discloses that the carotid rete mirabile in the giraffe has a poor sympathetic innervation. In contrast, the efferent artery of the rete (internal carotid artery) and the cerebral arteries show moderate sympathetic innervation. A certain degree of regional variability was noted in which the rostral arteries (anterior and middle cerebral) receive more sympathetic nerves than the caudal (posterior communicating and basilar) arteries. The sympathetic nerves on the giraffe cerebral vessels may constitute part of a host of mechanisms by which regional blood flow to the brain is regulated. Conversely, the paucity of sympathetic innervation of the carotid rete mirabile may indicate that this structure does not play an active role in vasoconstrictor responses during postural changes of the head.