Experimental Branch Research Articles

Cholecystokinin Octapeptide's Effect on Local Cerebral Glucose Utilization in the Laboratory Rat

Annals of the New York Academy of SciencesVolume 448, Issue 1 p. 663-665 Cholecystokinin Octapeptide's Effect on Local Cerebral Glucose Utilization in the Laboratory Rat C. A. TAMMINGA, C. A. TAMMINGA Maryland Psychiatric Research Center University of Maryland Baltimore, Maryland 21228Search for more papers by this authorG. LUCIGNANI, G. LUCIGNANI Laboratory of Cerebral Metabolism National Institute of Mental Health Bethesda, Maryland 20205Search for more papers by this authorL. J. PORRINO, L. J. PORRINO Laboratory of Cerebral Metabolism National Institute of Mental Health Bethesda, Maryland 20205Search for more papers by this authorT. N. CHASE, T. N. CHASE Experimental Therapeutics Branch National Institute of Neurological and Communicative Disorders and Stroke Bethesda, Maryland 20205Search for more papers by this author C. A. TAMMINGA, C. A. TAMMINGA Maryland Psychiatric Research Center University of Maryland Baltimore, Maryland 21228Search for more papers by this authorG. LUCIGNANI, G. LUCIGNANI Laboratory of Cerebral Metabolism National Institute of Mental Health Bethesda, Maryland 20205Search for more papers by this authorL. J. PORRINO, L. J. PORRINO Laboratory of Cerebral Metabolism National Institute of Mental Health Bethesda, Maryland 20205Search for more papers by this authorT. N. CHASE, T. N. CHASE Experimental Therapeutics Branch National Institute of Neurological and Communicative Disorders and Stroke Bethesda, Maryland 20205Search for more papers by this author First published: July 1985 https://doi.org/10.1111/j.1749-6632.1985.tb29981.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume448, Issue1Neuronal CholecystokininJuly 1985Pages 663-665 RelatedInformation

Predictions by Two One-Dimensional Cloud Models: A Comparison

Abstract Two one-dimensional steady-state models of cumulus convection in common use in weather modification research, the NOAA Experimental Meteorology Branch model (EMB) and the Great Plains Cumulus Model (GPCM), differ in their formulations in several ways. Some of the differences arise from the conceptualization of the convective phenomenon which is modeled in each and some from the physical parameterizations utilized. Predictions of cloud top and dynamic modification potential (seedability) by the two models for 57 midday radiosondes in the Midwest, differed significantly, with the EMB values consistently higher. GPCM simulations provided a better overall estimate of observed radar echo tops, while EMB consistently overestimated, by largest amounts when tops were below 12 km. Study of the impact of temporal and/or spatial separation between sounding and cloud area emphasizes the need, in the Midwest, to consider factors other than thermodynamic stratification (e.g. forced lifting, convergence) on the...

Cardiodynamic effects of experimental right bundle branch block in canine hearts with normal and hypertrophied right ventricles

Cardiodynamic effects of acute experimental right bundle branch block (RBBB) were studied in canine hearts: group A included 15 normal hearts; group B-1 had seven hearts with mild right ventricular hypertrophy (RVH), and group B-2 had 11 hearts with marked RVH. The main sequential changes following RBBB were marked prolongation of the Q upstroke interval of the right ventricle and striking shortening of right ventricular systolic time that affected right and left ventricular interaction, particularly in the hearts with RVH. Hemodynamic changes were: the right ventricular end-diastolic pressure was elevated markedly (4.4 ± 2.2 → 9.8 ± 2.6 mm Hg, p < 0.001) in group B-2, moderately ( p < 0.01) in group B-1, and not at all in group A. The right ventricular positive peak dp dt decreased remarkably (1036 ± 151 → 827 ± 152 mm Hg/sec, p < 0.001) in group B-2 and negligibly in the other groups. A significant correlation existed between the percentage of decrease in right ventricular peak dp dt and the QRS duration of RBBB in each group ( p < 0.01). The left ventricular peak negative dp dt decreased distinctly (2570 ± 326 → ± 2055 ± 362 mm Hg/sec, p < 0.01) in group B-2 and not at all in the other groups. The atroke volume showed 12% decrease in group B-2 ( p < 0.001), 8% decrease in group B-1 (NS), and no decrease in group A. In the presence of RVH, acute RBBB causes significant impairment of right and left ventricular function. The magnitude of the impairment invariably depends upon both the prior degree of RVH and the width of the QRS complex.

Transvenous angioplasty of experimental branch pulmonary artery stenosis in newborn lambs.

A dilatable form of bilateral branch pulmonary artery stenosis was created in 27 newborn lambs. Nine lambs were long-term survivors and were dilated with modified Grüntzig balloon dilation catheters. They were allowed to recover for 6-9 weeks, during which time there was no significant change in the mean systolic gradients across the narrowed sites. Thirteen arteries underwent dilation. Dilation was associated with a decrease in the systolic gradient in all cases (from 34.9 mm Hg to 8.1 mm Hg) and an increase in the diameter of the narrowed site (from 4.6 to 7.6 mm) as estimated by angiography. Flows and flow distribution were measured in four lambs before and after unilateral dilation using 15-mu radiolabeled microspheres; in each case, the fraction of total flow to the dilated lung rose after dilation (19.2 to 45.4%), as did the total flow to the dilated lung (30.0 to 69.2 ml/kg-min). Four lambs were catheterized every 2-4 weeks for an average of 16 weeks after dilation; the average gradient in these lambs remained below 10 mm Hg despite considerable growth (from 9.6 to 25.9 kg). Gross pathologic examination showed an intact vascular adventitia in all cases; there were multiple linear tears in the intima in recently (less than 7 days) dilated cases, but complete intimal healing had occurred by 2 months after dilation. No significant morbidity could be attributed to the dilation procedure. These results indicate that clinical trials are warranted.

Body surface isopotential maps of experimentally induced transient right bundle branch block.

The characteristic patterns of the epicardial activation and body surface isopotential maps (MAPs) were examined in experimental transient right bundle branch block (RBBB) produced by pressing the main stem of right bundle mechanically. During the recovery from the complete block, various degrees of incomplete RBBB (IRBBB) were obtained. The epicardial activation of IRBBB spread in almost normal fashion with delayed right ventricular epicardial breakthrough. And the MAPs manifested intermediate patterns between those obtained in control and in complete RBBB (CRBBB). The MAP patterns of IRBBB were classified into the following 3 groups by the difference of the localized bend of isopotential lines reflecting the epicardial breakthrough. In the advanced IRBBB with QRS prolongation over 25%, the epicardial breakthrough of the left ventricle was detected on the MAPs. In the moderate IRBBB with QRS prolongation around 20%, in addition to the left ventricular breakthrough the right ventricular breakthrough was detected at the center of the anterior chest. In the mild IRBBB with QRS prolongation less than 15%, only the right ventricular breakthrough was detected. These findings indicate usefulness of MAPs for diagnosing the severity of IRBBB due to the damage to the main right bundle. Moreover, these MAP patterns in IRBBB of main right bundle can be distinctly differentiated from the IRBBB MAPs resulting from incisional interruption of lateral branches of right bundle. The present findings also suggest the usefulness of MAPs in diagnosing the site of the conduction disturbance resulting in IRBBB.

Experimental retinal branch vein occlusion in rhesus monkeys. II. Retinal blood flow studies.

Experimental branch vein occlusion by laser photocoagulation in the rhesus monkey leads to early, marked, and lasting reduction of blood flow to the affected retinal region. The radioactive microsphere method demonstrates this reduction of blood flow in both gamma counting and autoradiography. The reduction of flow becomes evident as early as 2 hours after occlusion and persists up to 1 week. The mechanism of the altered flow is discussed.

Experimental retinal branch vein occlusion in rhesus monkeys. III. Histopathological and electron microscopical studies.

Experimental retinal vein occlusion in monkeys was followed by an immediate increase in capillary permeability which was accompanied by retinal oedema. This functional capillary change was followed at about 6 hours after occlusion by structural damage to the capillary wall. Thrombus formation occurred in the damaged vessels, and areas of stasis were thus produced with associated retinal haemorrhages. Finally, there was complete loss of the capillary endothelium and pericytes, and the acellular capillaries were invaded by proliferating glial cell processes, so producing permanent capillary closure.

Experimental retinal branch vein occlusion in rhesus monkeys. I. Clinical appearances.

Branch and hemisphere vein occlusion were produced in rhesus monkeys by argon laser photocoagulation. The following observations were made: (1) Immediately after occlusion there was venous dilatation, delayed filling of the artery, delayed drainage by the occluded vein, and capillary leakage. (2) Two patterns of evolution were identified within the first week. In some animals the fundus changes resolved and the retina returned to normal, while in others there was progressive retinal capillary closure. (3) Those animals destined to have capillary closure had diffuse or cluster retinal haemorrhages at 24 hours. (4) Capillary closure took place over 1 week and was usually complete over large areas of retina. (5) Retinal atrophy and major vessel changes occurred over several weeks. (6) Retinal revascularisation occurred in those areas of closure, though this was often limited. It was concluded that the early changes mimicked those seen in human retinal vein occlusion, though persistent retinal oedema and preretinal neovascularisation were not identified.

Hemodynamic effects of experimental right bundle branch block pattern

Hemodynamic effects of experimental right bundle branch block pattern

Photocoagulation in the treatment of retinal branch vein occlusion.

Australian Journal of OpthalmologyVolume 2, Issue 1 p. 5-9 Free Access Photocoagulation in the Treatment of Retinal Branch Vein Occlusion James D. Cairns D.O., F.R.C.S. (Ed.), F.R.C.S., F.R.A.C.S., Corresponding Author James D. Cairns D.O., F.R.C.S. (Ed.), F.R.C.S., F.R.A.C.S. The Prevention of Blindness Unit of the Melbourne University Department of Ophthalmology, and the Ophthalmic Research Institute of Australia at the Royal Victorian Eye and Ear Hospital, MelbourneDepartment of Ophthalmology, University of Melbourne, 32 Gisborne Street, East Melbourne, Victoria, 3002Search for more papers by this author James D. Cairns D.O., F.R.C.S. (Ed.), F.R.C.S., F.R.A.C.S., Corresponding Author James D. Cairns D.O., F.R.C.S. (Ed.), F.R.C.S., F.R.A.C.S. The Prevention of Blindness Unit of the Melbourne University Department of Ophthalmology, and the Ophthalmic Research Institute of Australia at the Royal Victorian Eye and Ear Hospital, MelbourneDepartment of Ophthalmology, University of Melbourne, 32 Gisborne Street, East Melbourne, Victoria, 3002Search for more papers by this author First published: February 1974 https://doi.org/10.1111/j.1442-9071.1974.tb01656.xCitations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat References Campbell, C. J., and Wise, G. N. (1973), “Photocoagulation Therapy in Branch Vein Obstructions”, Amer. J. Ophthal., 75: 28. Cleasby, G. W. (1972), “Photocoagulation of Macular Disease”, Trans. Asia-Pacific Acad. Ophthal. (In press). Clements, D. B., Elsby, J. M., and Smith, W. D. (1968), “Retinal Vein Occlusion: A Comparative Study of Factors Affecting the Prognosis Including a Therapeutic Trial of Atromid-S in this Condition”, Brit. J. Ophthal., 52: 111. Dayton, G, O. Jar, (1968), “The Value of photocoagulation in Occlusive Vascular Disease of the Retina”, Pacif. Med. Surg., 76: 26. Duff, I. F., Falls, H. F., and Linman, J. W. (1961), “Anticoagulant Therapy in Occlusive Vascular Disease of the Retina”, Arch. Ophthal., 46: 601. Foster Moore, R. (1924), “Retinal Vein Thrombosis Brit. J. Ophthal., Monograph, suppl. 2. Jensen, V. A. (1936), “Clinical Studies of Tributary Thrombosis in the Central Retinal Vein”, Acta Ophthal., Suppl. 10: 1. Kohner, E. M. et al. (1970), “Experimental Retinal Branch Vein Occlusion”, Amer. J. Ophthal., 69: 778. Krill, A. E., Archer, D., and Newell, F. W. (1971), “Photocoagulation in Complications Secondary to Branch Vein Occlusion”, Arch. Ophthal., 86: 48. Wetzig, P. C. (1969), “ Diabetic Retinopathy”, Pan-Pacific Surgical Association Eleventh Congress on Ophthalmology. (October, 1969.). Wise, G. (1967), “Macular Changes after Venous Obstruction”, Arch. Ophthal., 68: 544. Zweng, H. C., Little, H. L., and Peabody, R. R. (1969), “ Laser Photocoagulation and Retinal Angiography”, The C. V. Mosby Co., St. Louis , 134. Zweng, H. C., and Little, H. L. (1972), “ Argon Laser Photocoagulations of Retinal Vein Occlusions”, Presented to the Meeting of the Gonin Society, Miami, Florida, U.S.A. Citing Literature Volume2, Issue1February 1974Pages 5-9 ReferencesRelatedInformation

Retinal vascular occlusion in the cat by photocoagulation: Trial of a new instrument

The introduction of a small portable clinical instrument, the O'Malley Log 2 Xenon light coagulator, prompted a brief assessment of its value as a laboratory tool in the study of experimental vascular disease. Six cats were studied, two acutely and four after varying periods of survival up to 39 days. The results in general were similar to those of the only other comprehensive study of experimental branch retinal vein occlusion by photocoagulation, which was carried out on the pig and monkey. In particular the cat showed less acute reaction to the occlusions, but developed a well marked system of peripheral anastomotic vessels with accompanying haemorrhages in survival experiments. The status of the instrument, and these preliminary results are briefly discussed.

Tryptophan hydroxylase and serotonin in spinal cord and brain stem before and after chronic transection.

Journal of NeurochemistryVolume 18, Issue 8 p. 1593-1596 Tryptophan hydroxylase and serotonin in spinal cord and brain stem before and after chronic transection B. V. Clineschmidt, B. V. Clineschmidt Section on Biochemical Pharmacology, Experimental Therapeutics Branch, National Heart and Lung Institute, National Institutes of Health, Bethesda, Maryland 20014.Search for more papers by this authorJ. E. Pierce, J. E. Pierce Section on Biochemical Pharmacology, Experimental Therapeutics Branch, National Heart and Lung Institute, National Institutes of Health, Bethesda, Maryland 20014. Laboratory of Kidney and Electrolyte Metabolism, National Heart and Lung Institute.Search for more papers by this authorW. Lovenberg, W. Lovenberg Section on Biochemical Pharmacology, Experimental Therapeutics Branch, National Heart and Lung Institute, National Institutes of Health, Bethesda, Maryland 20014.Search for more papers by this author B. V. Clineschmidt, B. V. Clineschmidt Section on Biochemical Pharmacology, Experimental Therapeutics Branch, National Heart and Lung Institute, National Institutes of Health, Bethesda, Maryland 20014.Search for more papers by this authorJ. E. Pierce, J. E. Pierce Section on Biochemical Pharmacology, Experimental Therapeutics Branch, National Heart and Lung Institute, National Institutes of Health, Bethesda, Maryland 20014. Laboratory of Kidney and Electrolyte Metabolism, National Heart and Lung Institute.Search for more papers by this authorW. Lovenberg, W. Lovenberg Section on Biochemical Pharmacology, Experimental Therapeutics Branch, National Heart and Lung Institute, National Institutes of Health, Bethesda, Maryland 20014.Search for more papers by this author First published: August 1971 https://doi.org/10.1111/j.1471-4159.1971.tb00021.xCitations: 45 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume18, Issue8August 1971Pages 1593-1596 RelatedInformation

Experimental Retinal Branch Vein Occlusion

Experimental Retinal Branch Vein Occlusion

LOCAL AND TRADITIONAL VARIETIES OF DURUM WHEAT FROM THE AZERBAIJAN IN THE SOUTH DAGESTAN CONDITIONS

Studies on durum wheat were carried out in 2018–2020 on experimental plots of the Dagestan experimental station branch of the VIR. The climatic conditions were typical over the past decade due to global warming: warm autumn, almost no snow in winter, early spring and dry summer. Sowing was carried out in the third decade of October for vegetable predecessors (beet seed plants), where increased doses of complex fertilizers (nitrogen and phosphorus) were applied. Warm and wet conditions of winter and spring, two water-charging irrigations in autumn and vegetative in spring, as well as a top dressing with ammonium nitrate (2.0 c / ha) in the phase of the beginning of tube emergence contributed to the formation of good stalks and productive ears of plants. In total 458 samples of the durum wheat world collection from the mountain, foothill and plain zones of Azerbaijan for breeding and valuable traits have been studied: early maturity, resistance to fungal diseases, productivity and its components. Highlighted productive varieties of durum wheat with a high adaptive potential, which can be used both for purely genetic research and in practical breeding to improve existing varieties and develop new ones.

Ventricular epicardial activation studies in experimental and spontaneous right bundle branch block in the dog

The time and sequence of right ventricular epicardial activation were determined by measuring the onset of activation at 27 representative sites. Studies were performed on normal and experimental dogs, 1 dog with spontaneous complete right bundle branch block, 1 with spontaneous incomplete right bundle branch block and 1 with an atypical configuration of the QRS complex. In both experimental and spontaneous complete and incomplete right bundle branch block, the total right ventricular epicardial activation time was prolonged beyond that found in the control dogs. The sequence of right ventricular epicardial activation in the spontaneous cases of right bundle branch block was not different from that found in the normal dogs; however, in experimentally produced complete right bundle branch block, the sequence was altered so that earliest activity occurred along the dorsal interventricular sulcus. In both experimental and spontaneous incomplete and complete right bundle branch block, many of the right ventricular epicardial sites were activated later in the QRS complex than in normal dogs.

Dependence of ventricular distensibility on filling of the opposite ventricle.

Dependence of ventricular distensibility on filling of the opposite ventricle.

PARAPHENYLENEDIAMINE STAINING OF OSMIUM-FIXED, PLASTIC-EMBEDDED TISSUE FOR LIGHT AND PHASE MICROSCOPY

Journal Article Technical Note Paraphenylenediamine Staining of Osmium-Fixed, Plastic-Embedded Tissue for Light and Phase Microscopy Get access Juan F. Estable-Puig, M.D., Juan F. Estable-Puig, M.D. Washington, D. C. ‡UCP Fellow on leave of absence from Facultad de Medicina, Montevideo, Uruguay; Present Address: Experimental Pathology Branch, Ames Research Center, NASA, Moffett Field, California. Search for other works by this author on: Oxford Academic PubMed Google Scholar Walter C. Bauer, Capt., M.C., USA., Walter C. Bauer, Capt., M.C., USA. Washington, D. C. §Present Address is Washington University School of Medicine, St. Louis, Missouri. Search for other works by this author on: Oxford Academic PubMed Google Scholar J. M. Blumberg, Brig., Gen., M.C., USA. J. M. Blumberg, Brig., Gen., M.C., USA. Washington, D. C. Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Neuropathology & Experimental Neurology, Volume 24, Issue 3, July 1965, Pages 531–535, https://doi.org/10.1097/00005072-196507000-00012 Published: 01 July 1965

An analysis of waves in a two-layer composite plate and its application to surface wave propagation experiments on roads

In this paper a derivation is given of the theoretical dispersion curves relating phase velocity and wavelength of waves in a two-layer composite plate in which stresses and displacements are continuous across the interface. Computations are carried out for different ratios of shear moduli and thickness of the two media in the composite plate using a computer programme which is capable of deriving the real roots of the dispersion equation of waves in layered plates or a layered half-space with up to thirty layers. It is shown that part of the dispersion curve of flexural waves in the composite plate can be derived to an accuracy of 5 % in the wavelength by adding the wavelengths of the antisymmetric or flexural modes of the individual plates at each velocity. This approximation applies over a fairly wide range of shear modulus ratios (4:1 to 1: 2) and for a ratio of thickness of 2:7. The computations of the dispersion curves in free composite plates are shown to give an acceptable approximation to many features of the experimental flexural wave branch of the dispersion curves obtained on roads which have two upper layers of considerably higher shear moduli than the underlying media. Thus, the computational analysis provides a basis for obtaining the thicknesses and elastic properties of the upper layers of many types of road construction from the experimental dispersion curves.

Studies on the Soft-Textured Rice Kernel : VIII. Kinds of soil texture and the three essential elements of fertilizer in the formation of soft-textured rice kernel

In our experiment of 1958 we cultivated Norin. No. 1 in the testing farm of the University of Fukui under our standard method of cultivation. We used a/5, 000 Wagner pots (placing 10 pots in each plot) and experimented with three kinds of soil for cultivation : 1) cultivated soil (clay loam) from the paddy-field of our farm, 2) refined heavy clay (dia. less than 0.01mm), and 3) sandy soil (coarse sand with dia. 2.0-0.2mm.) from the river bed. As basic fertilizer we gave on May 20 3 g of ammonium sulfate, 4 g of calcium superphosphate, and 1.4 g of potassium chloride per pot. Transplanting the seedlings under standard culture (50-day seedlings aged 6.5 leaves, 3 seedlings per hill per pot) on May 21, we then proceeded to give them additional fertilizer, 0.6 g of ammonium sulfate on June (in the tillering stage) and 0.4 g of the same on July 1 (in the early ear-forming stage). Thus our experiment was fed by conducted under our standard cultivation with the use of three elements of fertilizer above-stated, fed by the water of our city aqueduct. Further, in order to produce rice grain, we applied half of the whole volume of fertilizer on those plots with sandy soil and heavy clay, where no fertilizer was given. Then collecting the ripe ears in the whole 10 pots of each plot, we selected unpolished rice grains of standard quality, putting them to quantitative analysis. In our experiment of 1959, in the testing rice-fields of the University of Fukui and the Prefectural Agricultural Experimental Branch Station of Osaka (the soil is CL in both places), we used two varieties Norin No.1 and Yutakasenbon to proceed with the same kind of fertilization experiment as before. For each testing field (0.1 a per plot in 2 blocks) we took standard culture as basis (three elements per plot), going through the same process of selection and quantitative analysis. The results of the analysis showed some variations in different pots, but the property of rice kernel in each plot in Fukui proved soft-textured in its constituent ratio, no plot showing a change from soft-textured to hard-textured rice kernel. In Osaka, conversely, no plot showed any change from hard-textured to soft-textured kernel. We conclude from our experiments that the kinds of soil texture and the three elements of fertilizer in the formation of both soft-and hard-textured rice kernel have nothing to do with the varieties of specimens. In other words, we have confirmed that so far as the minimum amount of three elements of fertilizer is present necessary to produce standard rice grains, the texture of rice kernel is free from the influence of any element of fertilizer and any kind of soil texture.

Experimental right bundle branch block in the normal human heart: Electrocardiographic, vectorcardiographic and hemodynamic observations ∗

1. 1. Right bundle branch block was experimentally produced in twenty normal subjects by applying pressure on the right ventricular septal surface with an electrode-catheter. Electrocardiographic, vectorcardiographic and hemodynamic observations were performed in varying degrees of right bundle branch block obtained in this way. 2. 2. The results of these experimental studies in man are in agreement with the current criteria for the diagnosis of right bundle branch block of advanced degree (complete right bundle branch block), but new and valuable information has been obtained concerning the minor degrees of right bundle branch block (incomplete right bundle branch block). 3. 3. Morphologic changes are more important than quantitative data for the electrocardiographic and vectorcardiographic diagnosis of incomplete right bundle branch block. A QRS duration of only 0.07 or 0.08 second can be associated with minor degrees of right bundle branch block. Slowing of the QRSsÊ loop is not always present in these cases, and the relationship between electrical and mechanical systole remains frequently within normal variations. 4. 4. Right bundle branch block of advanced and minor degrees is an experimental reality in human beings. On the other hand, the remarkable similarity between the experimental and clinical findings constitutes a valuable support of the hypothesis which explains the complete and incomplete right bundle branch block patterns, seen frequently in clinical practice, by right bundle branch involvement. However, it does not mean that a late R wave in the right precordial leads results always from this mechanism. 5. 5. A surprising similarity is noted when the electrocardiographic and vectorcardiographic changes developing during the regression from experimental right bundle branch block are compared with those observed following surgical repair of atrial septal defects with mild pulmonary hypertension or without pulmonary hypertension. It is believed that right bundle branch block in regression could be an electrogenic factor in these postoperative changes.