Glomerular Patterns Research Articles

Importance of angiogenic action of angiotensin II in the glomerular growth of maturing kidneys

We studied the effect of three antihypertensive drugs on the growth of glomeruli in four- to five-week-old Munich-Wistar rats (N = 24), which were undergoing rapid maturation processes. Young rats were given an angiotensin converting enzyme inhibitor (ACEI, enalapril, 50 mg/liter drinking water), verapamil (50 mg/liter) or hydralazine (80 mg/liter) or no treatment for six weeks. Body weight increased comparably in the treatment groups and age-matched controls, reaching on average 197 +/- 11, 214 +/- 12 and 198 +/- 3 g in ACEI-, verapamil- and hydralazine-treated rats, respectively, versus 218 +/- 6 g in control rats. Glomerular hemodynamic patterns, including glomerular capillary pressure, measured in maturing rats after one and six weeks of ACEI treatment were unaffected by ACEI. Mean planar area of glomeruli (PAmean) achieved was smaller than control in ACEI rats (6.60 +/- 0.20 x 10(-3) mm2 vs. 5.37 +/- 0.22, respectively, P less than 0.005), but not in rats treated with other antihypertensive drugs. Furthermore, the maturational PAmean increase in rats given ACEI for six weeks was, on average, only half of that achieved by age-matched controls not given ACEI, in contrast to normal maturational growth with hydralazine or verapamil (29% increase in PAmean from normal baseline in ACEI vs. 52%, 53% and 59% increases in verapamil, hydralazine and control, respectively). In contrast, comparable PAmean values were found in adults with (7.08 +/- 0.22 x 10(-3)mm2, N = 6) and without (6.98 +/- 0.33 x 10(-3)mm2, N = 6) ACEI treatment given for six weeks. Therefore, ACEI, but not verapamil and hydralazine, causes growth retardation in maturing glomeruli.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of antihypertensive drugs on glomerular morphology

We quantitated the glomerular size and the degree of sclerosis simultaneously in individual glomeruli with the use of three-dimensional histological analysis on serial sections obtained from remnant kidneys with highly heterogeneous glomerular lesions after subtotal nephrectomy (sNPX). Four to six weeks after sNPX (Group I, N = 7), 90% of glomeruli had mild sclerosis (sclerosis index, SI; less than 1.5 on a 0 to 4 scale) with a strong positive correlation between the maximum planar area of glomerulus (PAmax) versus SI. Twelve weeks after sNPX (Group II, N = 6) more than 50% of glomeruli had advanced sclerosis (average SI:1.88), and a significant positive correlation was again found between PAmax and SI in glomeruli with mild to modest sclerosis (SI less than 1.5), whereas these two variables were correlated inversely in glomeruli with advanced sclerosis. Administration of enalapril (50 mg/liter drinking water) or hydralazine (200 mg/liter) + hydrochlorothiazide (50 mg/liter) for 12 weeks (Group III, N = 12) markedly attenuated the sclerosis to comparable degrees (average SI: 0.15 vs. 0.22). The former antihypertensive therapy decreased glomerular capillary hydraulic pressure (PGC) to normal range, whereas the latter triple drug therapy was largely without effect on PGC. Of note, the positive correlation between SI and PAmax remained unaffected by these anti-hypertensive drugs. SI of the glomeruli from both treated groups was expressed as a first-order function of PAmax. The correlation coefficient is identical to that found in non-treated Group II remnant glomeruli, so that the degree of sclerosis is mathematically uniquely correlated with the glomerular size, regardless of drug treatment. Thus, within a given remnant kidney, the magnitude of glomerular hypertrophy has a direct correlation with the degree of sclerosis, while the altered glomerular hemodynamic pattern has little modulatory role in determining the magnitude of this hypertrophy. Enalapril and triple drug therapy, at equi-depressor doses in regard to systemic blood pressure, had identical potency in sparing glomerular structure. The primary determinant for this antisclerotic potency appears to be related to the drugs' potency to inhibit glomerular growth rather than an effect on the abnormal hemodynamics which develop in the glomerulus.

Development of glomerular pattern visualized in the olfactory bulbs of living mice

Many regions of the mammalian brain are characterized by iterated ensembles of nerve cells which can be distinguished anatomically and physiologically. A particularly striking example is the pattern of glomeruli in the olfactory bulbs; other instances are columns and 'blobs' in the visual cortex, barrels and columns in the somatosensory cortex, and striasomes and cell islands in the neostriatum. Understanding the generation of these neuronal ensembles has a bearing on a variety of important neurobiological problems, including the nature of critical periods, the age-dependent response of the nervous system to injury and the manner in which neural information is stored. Analysis of these issues has usually been restricted to studies of the brains of different individuals at various ages. Many questions about the formation of such units, however, can only be answered by observing the same brain repeatedly in a living animal. This strategy would enable a direct assessment of how these units are assembled, whether the initial ensembles persist and whether units are lost or gained as an animal matures. We have succeeded in studying the pattern of glomeruli in the mouse olfactory bulb on two separate occasions during postnatal development. Comparison of the patterns observed at intervals of up to three weeks show that this part of the brain is gradually constructed by the addition of new glomeruli to a persisting population.

Histomorphological variations in systemic AA amyloidosis: clues of AA protein polymorphism.

The histological location of amyloid within various organs in 25 cases of systemic AA amyloidosis was studied with a view to determine whether different morphological patterns exist in this category of amyloidosis. Although morphological variations due to progressive severity of disease were observed, there were appreciable variations in the patterns of amyloid deposition in the kidney and spleen that could not be simply explained on those grounds. Eleven (61%) of 18 kidneys examined showed severe glomerular involvement with mild degrees of vascular deposition while the remaining seven showed predominantly vascular involvement. The glomerular pattern appeared to be more ominous, being significantly associated with severe proteinuria or chronic renal failure. In nine (69%) of 13 spleens examined, amyloid was confined to the walls of small and medium-sized arteries while in the remaining four, vascular involvement was less severe and amyloid was deposited mainly along the reticulin of the white pulp. Possible explanations for these different patterns included resorption and redistribution of amyloid within the body during the course of the disease, and variation in tissue deposition as a manifestation of polymorphism of amyloid proteins. The latter appeared more feasible in view of the recent demonstration of SAA polymorphism and AA heterogeneity in man.

Renal function in Sudanese school children withSchistosoma mansoni infection

Renal function was investigated in 218 school children with Schistosoma mansoni infection in the Providence of Gezira in central Sudan and in 65 Sudanese and 65 German age-matched controls. Serum creatinine was normal in all children. A pathological urinary protein-creatinine ratio was found in 3% of S. mansoni-infected children and in 5% of Sudanese controls but in none of the European children. Characterization of pathological proteinuria using albumin nephelometry, alpha-1 microglobulin immunodiffusion and SDS-polyacrylamide gel electrophoresis in these children showed glomerular, tubular or mixed glomerulotubular patterns. One, 4 and 6 months following treatment of schistosomiasis with praziquantel, stools were re-examined; 57% of patients were cured, 16% were found to be reinfected and 27% had persistent egg excretion. Six months after therapy, pathological urinary protein-creatinine ratios were encountered in 3% of S. mansoni patients and in none of the 34 reinvestigated controls. Proteinuria was similar in patients with persistent S. mansoni egg excretion and in children cured of schistosomiasis infection. It is concluded that there was no evidence for S. mansoni associated glomerulonephritis in this group of Sudanese children. The high rate of pathological proteinuria in S. mansoni-infected and non-infected Sudanese children may be due to other causes.

Specificity of spatial patterns of glomerular activation in the mouse olfactory bulb: computer-assisted image analysis of 2-deoxyglucose autoradiograms

We have developed a computer-assisted method for analyzing the 2-deoxyglucose (2-DG) autoradiograms of mice olfactory bulbs. The purpose of the study was to numerize the maps of glomerular activation in order to achieve a statistical comparison of the glomerular patterns evoked by different stimuli. The spatial distribution of glomerular activation was displayed on unfolded representations of the glomerular layer which were built up using glomerular optical densities (OD) measured systematically within 13 sections per bulb. Each bulbar sample was converted into an ‘OD profile’. A matrix composed of 18 OD profiles was submitted to a principal component analysis. The first factor which accounted for 28% of the variance separated unambiguously two clusters corresponding to the bulbs issued from animals stimulated with amylacetate and isovaleric acid, respectively. The second and third factors which accounted for 14% and 12% of the variance segregated the control group (animals exposed to pure air) from the odor-stimulated ones. It was demonstrated that the cluster separation was actually due to the specific spatial distribution of the most-labelled glomeruli. A particular attention was paid to the well-delineated glomerular activation evoked by isovaleric acid. The results demonstrate the specificity and reliability of the glomerular 2-DG patterns. The method should be useful for further comparisons of patterns elicited by larger sets of odorant compounds.

Complement membrane attack (MAC) in idiopathic IgA-glomerulonephritis

Antigens of the membrane attack complex of complement (MAC), such as C5, C6, C9 and MAC-related neoantigen(s), were demonstrated in the mesangium of 23 cases with IgA-glomerulonephritis (IgA-GN) and two cases with Henoch-Schönlein purpura nephritis (HSP). High specificity of the polyclonal antibodies was verified by dot-blot analysis. Control specimens lacking immunoglobulin deposits were negative for MAC-related antigens. Markers of classical pathway activation (Clq and C4) were observed only in two of 24 and one of 23 cases of IgA-GN and HSP, respectively. Glomerular distribution patterns (mesangial vs. mesangio-peripheral) of immunoglobulin or complement deposits were correlated for IgA and C3b/iC3b (P less than 0.002), for IgA and properdin (P less than 0.002) and for IgA and MAC neoantigens (P less than 0.01). Double immunostaining experiments revealed co-localization of IgA and MAC neoantigens at identical mesangial and capillary sites. Glomerular distribution of the less pronounced IgG or IgM deposits did not correlate with that of any complement-derived antigen. The pattern of MAC-related antigens was found to be uniformly either mesangial or mesangio-peripheral. Staining for MAC-related antigens was less intense in IgA-GN cases with minimal glomerular lesions than in cases with more advanced non-sclerosing lesions. IgA, C3d, and MAC localized in corresponding glomerular sites. This is consistent with complete local activation of complement by glomerular IgA deposits via the alternative pathway. The possibility exists that MAC plays a pathogenetic role, such as by irritation of bystander cells, in IGA-GN and HSP.

Sensory Nerve Endings in the Mucosa of the Epiglottis—Morphologic Investigations with Silver Impregnation, Immunohistochemistry, and Electron Microscopy

This study was conducted in order to investigate the structure of sensory nerve endings of the human epiglottis and substance P immunoreactive nerve fibers of the canine epiglottis in relationship to physiologic functions of the larynx. The human epiglottis was observed by light microscopy (silver impregnation) and electron microscopy, and the canine epiglottis was studied by peroxidase-anti-peroxidase (PAP) immunohistochemistry. The results are summarized as follows: (1) In the membranes of the epiglottis, we observed free endings of simple or complex tree shape, corpuscle endings with glomerular patterns, and taste-bud-like structures, and (2) electron microscopic studies revealed varicosity of the terminal axon with processes that contained small, clear and large, dense cored vesicles. Substance P was observed in these structures, and it was suggested that substance P was related to perception in the larynx.

Role for angiotensin II in an overt functional proteinuria

A partial renal vein constriction (RVC) was induced acutely in Munich-Wistar rats. RVC caused a marked reduction in glomerular plasma flow rate, and rises in glomerular transcapillary hydraulic pressure difference and efferent arteriolar resistance. These changes were associated with a marked increase in urinary protein excretion, on average from a baseline level of 8 to approximately 120 mg/24 hrs per kidney. Infusion of saralasin, an angiotensin II (AII) antagonist, largely normalized these indices, including urinary protein excretion (to approximately 35 mg/24 hrs per kidney), despite continued RVC. In separate rats, fractional clearances of neutral [125I]dextrans (molecular radii = 18-60 A) (CDEX/CIN) were measured. RVC caused a significant increase in CDEX/CIN for large dextrans (greater than or equal to 44A), but not small dextrans (less than or equal to 42A). Saralasin infusion led to a partial return toward baseline values of CDEX/CIN for the large dextrans. On the basis of the heteroporous membrane theory for glomerular filtration, the glomerular sieving defect during RVC was attributed to an increase in the relative fluid flux through a group of large non-selective pores. A marked alteration in glomerular microcirculatory pattern induced by enhanced action of endogenous AII in turn seemed to account largely, although not entirely, for the impairment of glomerular size-selectivity during RVC.

Ultrathin‐layer sodium dodecyl sulfate‐polyacrylamide gradient gel electrophoresis and silver staining of urinary proteins

AbstractUltrathin‐layer sodium dodecyl sulfate‐polyacrylamide gradient gel electrophoresis in combination with silver staining is a highly sensitive and rapid method for molecular size analysis of urinary proteins. First results are achieved after 4 h (electrophoretic run, 100 min, followed by Coomassie Brilliant Blue staining, 2 h). After additional silver staining, including a recycling step, the results are ready for evaluation within 7 h. Urine samples do not need to be concentrated. Within a single gel, 25–27 samples can be run side by side under identical conditions and thus compared without ambiguity. By coelectrophoresis of pure proteins and immunological analysis 13 urinary proteins could be identified and for 7 of them the detection limits were determined. Glomerular protein patterns in samples of urine with a protein concentration in the normal range are compared with the concentration of albumin and transferrin measured by a sensitive enzyme immunoassay. Typical renal and extrarenal protein patterns are shown.

A new possibility to analyse urinary proteins: isoelectrofocusing with immobilized pH gradients.

As a new method for the analysis of proteinuria isoelectricfocusing with immobilized pH gradients is introduced. Ths new approach has several advantages over the conventional methods. The applicability is demonstrated by analysing the long-term changes in proteinuria of a 5/6 nephrectomized rat. Soon after 5/6 nephrectomy, a glomerular pattern of protein excretion predominates which later on is followed by a tubular pattern.

Spontaneous glomerular IgA deposition in ddY mice: An animal model of IgA nephritis

AbstractSpontaneous glomerular IgA deposition in ddY mice: An animal model of IgA nephritis. It was found that ddY mice derived from non-inbred dd-stock mice brought from Germany before 1920 and then raised in Japan developed spontaneously IgA dominant deposition in the glomerular mesangium. In this report we give a detailed natural history of the renal pathology of those mice. The animals were fed rodent laboratory chow and sacrificed in groups of 9 to 10 at 6, 10, 16, 24, 28, 40, and 59 weeks of age. The bladder urine was analyzed, serum immunoglobulins were measured, and the kidney specimens were evaluated with light, fluorescent, and electron microscopy. Proteinuria was (+) to (+ +) after 28 weeks and (++) to (+ + +) at 59 weeks with negative hematuria. Mesangial cell proliferation began to appear at 16 weeks, then progressed to a definite proliferative glomerulonephritis. At 59 weeks an additional increase of the mesangial matrix occurred. By immunofluorescence, there were IgG of (++), IgM (+) to (++), IgA (+) and C3 (+) in the glomeruli until 28 weeks. However, IgA started to be dominant at 40 weeks and the glomerular pattern was IgA (++) to (+ + +), IgG (+) to (++), IgM (±) to (+) and C3 (+) to (++) at 59 weeks. Polyclonal IgA and IgG2a among immunoglobulins steeply rose at 40 weeks, and at 59 weeks IgA increased by 850%, IgG2a by 280%, IgG1, by 170%, IgG2b by 90%, and IgM by 60%, as compared with their level at 6 weeks. There was no anti-nuclear antibody. Thus, ddY mice, at least after the age of 40 weeks, can be used as a new animal model for spontaneous IgA nephritis. The probable origin of IgA is also discussed.Dépôts glomérulaires spontanés d'IgA chez des souris ddY: Un modèle animal de néphrite à IgA. Il a été trouvé que des souris ddY dérivées d'un stock dd non inbred importées d'Allemagne avant 1920 puis élevées au Japon développaient spontanément des dépôts d'IgA dominants dans le mésangium glomérulaire. Nous donnons ici une histoire naturelle détaillée de l'anatomo-pathologie rénale de ces souris. Les animaux ont reçu un régime de laboratoire pour rongeurs, et ont été sacrifiés par groupes de 9 ou 10 à 6, 10, 16, 24, 28, 40, et 59 semaines d'age. Les urines vésicales ont été analysées, les immunoglobulines sériques mesurées et des échantillons rénaux examinés en microscopie optique, à fluorescence et électronique. La protéinurie était de (+) à (++) après 28 semaines et de (++) à (+ + +) à 59 semaines, sans hématurie. La prolifération cellulaire mésangiale commençait à apparaître à 16 semaines, puis progressait vers une glomérulonéphrite proliférative nette. A 59 semaines, une augmentation supplémentaire de la matrice mésangiale se produisait. En immunofluorescence, il y avait des IgG (++), des IgM (+) à (++), des IgA (+) et du C3 (+) dans les glomérules jusqu'à 28 semaines. Néanmoins, les IgA commençaient à prédominer à 40 semaines, et l'aspect glomérulaire était IgA (++) à (+ + +), IgG (+) to (+ +), IgM (±) à (+) et C3 (+) à (+ +) à 59 semaines. Parmi les immunoglobulines, les IgA polyclonales et les IgG2aaugmentaient fortement à 40 semaines, et à 59 semaines les IgA avaient augmenté de 850%, les IgG2a de 280%, les IgG1 de 170%, les IgG2b de 90%, et les IgM de 60% par rapport à leur niveau à 6 semaines. Il n'y avait pas d'anticorps antinucléaire. Ainsi, les souris ddY, au moins après l'age de 40 semaines peuvent être utilisés comme un nouveau modèle animal de néphrite à IgA spontanée.

Evaluation of Proteinuria by Two-Dimensional Polyacrylamide Gel Electrophoresis after Kidney Transplantation

Urinary proteins were studied in patients after kidney transplantation during various functional states (normal function, acute rejection, chronic rejection) by two-dimensional polyacrylamide gel electrophoresis. In the first dimension, the proteins were separated according to their electric charge by isoelectric focusing, and in the second dimension according to their molecular weight by sodium dodecyl sulfate polyacrylamide gel electrophoresis. After electrophoresis the proteins were visualized using a highly sensitive silver stain technique. The combination of these methods allowed the discrimination of up to 250 protein spots in human urine, most of them unidentified up to now. Functional changes of the kidney transplants were accompanied by complex changes of the protein pattern in urine. These changes cannot be simply compared to the tubular and glomerular pattern of proteinuria which can be identified by one-dimensional sodium dodecyl sulfate electrophoresis. The 2D electrophoresis of urinary proteins may develop into a useful tool in localizing of kidney damage and in the evaluation of renal disease.

Is renal involvement a prognostic parameter in patients with infective endocarditis?

Renal involvement (RI)--defined as proteinuria greater than 150 mg per 24 h with haematuria or impaired glomerular filtration rate--was studied in 80 patients with infective endocarditis (IE). Proteinuria was measured quantitatively and further differentiated by the SDS-polyacrylamide-gel electrophoresis. RI was found in 40 patients (50%) with proteinuria from 150 to 8000 mg per 24 h. SDS-PAGE revealed a tubular protein pattern in 17 patients, a glomerular pattern in 6 and a glomerulo-tubular pattern in 17. Mortality rate was significantly higher in patients with RI (40%) than in those without (7.5%), and was not related to the type of infected valve, infective organisms, method of treatment (surgical or medical) or embolic events. Following successful treatment of IE, 18 out of 23 patients showed complete normalization of renal function. Renal involvement in patients with IE may be of prognostic significance--indicating an impaired prognosis.

Evaluation of urinary proteins by sodium dodecyl sulphate polyacrylamide disc gel electrophoresis and molecular mass analysis

Patterns of urinary proteins were examined on sodium dodecyl sulphate polyacrylamide gels and compared to those obtained using high voltage agarose electrophoresis. Both were found to be well adapted to routine laboratory analysis although the former had more sensitivity for early renal changes. Glomerular, mixed and tubular patterns were identifiable, and special precautions and pitfalls whilst interpreting the latter were pointed out. Restricted α 1 antitrypsin was shown in renal transplant proteinuria and its possible mechanisms were discussed. Molecular masses and frequencies of several discrete bands in heavy proteinurics were calculated, and attempts to identify them were made with reference to standard proteins.

A study of scanning (SEM) and transmission (TEM) electron microscopy of the glomerular capillaries in developing rat kidney.

Kidneys of 2 to 10 day-old rats of Wistar and Sprague-Dawley strains were fixed with glutaraldehyde by retrograde vascular perfusion and then prepared for observation in TEM and SEM. In addition methacrylate casts of differentiating glomerular capillaries were examined by SEM. Although the glomerular vascular pattern differs from one glomerulus to another, its differentiation proceeds according to the following general plan. First the glomerular capillary splits longitudinally, finally to form 3 to 5 lobules consisting of a capillary network, sustained centrally by the mesangium. In the present study the differentiation of glomerular capillaries is described in five successive arbitrarily selected stages. At Stage I a capilllary loop penetrates between the lower limb and the middle segment of the S-shaped body, the rudimentary nephron. At Stage II the capillary undergoes a first subdivision, establishing the primitive lobulation of the glomerulus. At Stage III the vascular and urinary poles differentiate. At Stage IV the glomerulus assumes the aspect of a spherical body, and the capillaries in each lobule undergo subdivision. In Stage V the glomerular vascular pattern approaches its adult appearance, although the maturation processes continue for an extended period of time. Hence in the 10 day-old rat the best-differentiated glomeruli are half the size of adult glomeruli, and their capillary loops are proportionally less well-developed. The capillaries of adjacent lobules may communicate with each other, but a direct vascular shunt between the afferent and efferent vessels cannot be demonstrated.

Doublethink in Lupus Nephritis

Selecting a treatment strategy for azotemic patients with lupus nephritis is a stress-inducing exercise. It has been suggested that the type and extent of glomerular abnormalities offer the best guidance for therapy. Study of percutaneous renal biopsy specimens from patients with systemic lupus erythematosus (SLE) who have proteinuria, gross or microscopic hematuria, or a diminished creatinine clearance will in almost all instances discover pathological changes in glomeruli. Mild glomerular pathological changes transform to diffuse proliferative glomerulonephritis sufficiently frequently, however, to preclude constant association of a benign clinical course with a favorable biopsy specimen.1Changes from severe proliferative to membranous glomerulonephritis, from focal or diffuse proliferative glomerulonephritis to membranous glomerulonephritis, and from membranous to diffuse proliferative glomerulonephritis occur, indicating the folly of dogmatically ascribing any clinical syndrome to a fixed histological glomerular pattern. While it is generally true that development of diffuse proliferative glomerulonephritis in SLE is an ominous prognostic

Plasticity of connections of the olfactory sensory neuron: Regeneration into the forebrain following bulbectomy in the neonatal mouse

Neonatal mice underwent unilateral bulbectomy, which included the main and accessory olfactory bulbs. From 5 days of survival onward, there was a marked anterior displacement of the frontal cortex into the cavity previously occupied by the bulb. As a result of the bulbectomy and consequent damage to olfactory axons, the olfactory perikarya underwent retrograde degeneration. New neurons were then reconstituted from stem cells within the olfactory neuroepithelium. By 20 postoperative days the new olfactory axons had reached the level of the lamina cribrosa and by 30 days the fibers had penetrated into the telencephalon and had formed typical glomerular structures within the host tissue. Fibers were directed to either the paleo- or neocortex where they were observed in close proximity to large cortical neurons. The formation of glomeruli persisted over the course of the study (180 days) and showed an expansion within the cortical tissue up to 60 days of survival. The identification of these fibers and glomerular structures as olfactory was confirmed by immunohistochemical techniques using antisera to the specific olfactory protein. Ultrastructural observations clearly indicated the typical glomerular pattern of the structures and demonstrated synaptic contacts between the sensory terminals and dendritic processes, as yet unidentified, originating from the surrounding cerebral matrix. Our observations thus demonstrate that following bulbectomy and retrograde degeneration of olfactory neurons, the cells can regenerate in the absence of their normal target. Furthermore, the newly formed axons can penetrate a ‘foreign’ environment, the cerebral cortex, and form typical glomerular structures and corresponding sensory synapses. The findings suggest a heretofore unsuspected degree of plasticity in the olfactory system as well as in the cerebral cortex.

Evidence for a bilateral ‘glomerular’ projection from the red nucleus to the spinal nucleus of the trigeminal nerve in the cat

Following unilateral lesions in the rostral, dorsolateral portion of the red nucleus degenerating fibers were observed bilaterally in the spinal nucleus of the trigeminal nerve. Of particular note, the degeneration within the alaminar, parvocellular portion of the nucleus terminated in a striking glomerular pattern. Lesion of the caudal and medial portion of the red nucleus, or the tegmentum rostral and lateral to the red nucleus produced no such pattern of degeneration. The results demonstrate the existence of a previously unknown bilateral projection from the red nucleus to the spinal trigeminal complex in the cat.

Localized projection of olfactory nerves to rabbit olfactory bulb

The organization of the olfactory nerve projection was studied in the rabbit by making small lesions in the olfactory nerves. The distributions of degenerating olfactory nerve fibers and axon terminals in the olfactory bulb were identified using the Fink-Heimer and Eager selective silver methods, and the lesion sites were identified in transverse sections of the olfactory organ. The degeneration was localized in the olfactory nerve and glomerular layers of the ipsilateral bulb, and the projections from different regions in the olfactory epithelium had specific regional localizations in the glomerular layer. There were variations in the sharpness of the projections from different regions. Groupings of glomeruli showing levels of degeneration were observed. However, neighboring glomeruli often showed marked variations in intensity of degeneration, and normal glomeruli were present within regions containing degeneration. In many instances the degeneration was restricted to small fingers or patches within a single glomerulus. It is likely that the differing glomerular patterns indicate different levels of functional organization in the olfactory pathway.