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PubMed1979

The structure of A segments from glycerinated skeletal muscle.

The A band of skeletal muscle consists of an array of thick myosin-containing filaments along with non-myosin proteins such as C protein and M line protein. In order to study the arrangement of the myosin and non-myosin components, A segments which are aggregations of thick filaments held together at the M line were prepared from glycerinated chicken pectoral and rabbit psoas muscles and examined by electron microscopy. Details of the preparative technique and comparison of the morphologies of A segments and I segments are provided. The A segments from chicken pectoral muscle exhibited 11 to 12 stripes in each half lateral to the bare zone. Several less distinct bands as well as subdivisions of the individual stripes were also observed. The periodicity of the major stripes in the A segments was 424 +/- 10 A. The A segments prepared from rabbit psoas muscle had a periodicity of 432 +/- 13 A, but in contrast with chicken A segments, fewer rabbit A segments showed this periodicity. We conclude that A segments can be separated from glycerinated chicken and rabbit skeletal muscles and compare our results with those of others who prepared A segments from frog and rabbit skeletal muscles in the absence of glycerol.

Animals↗
PubMed1976

Total synthesis of the structural gene for the precursor of a tyrosine suppressor transfer RNA from Escherichia coli. 7. Enzymatic joining of the chemically synthesized segments to form a DNA duplex corresponding to the nucleotide sequence 1-26.

Duplex [I], which represents the nucleotide sequence 1-26 of the double-stranded DNA corresponding to the precursor for a tyrosine suppressor tRNA, has been synthesized by the enzymatic joining of five chemically synthesized deoxyribooligonucleotide segments. The synthesis was accomplished in two different ways. In a one-step synthesis, all of the five segments were used together: segments 2, 3, and 5 carried 5'-33P-labeled phosphate groups while segment 4 carried a 32P-phosphate group. An alternative, two-step method involved the joining of 5'-32P-phosphorylated segment 2 to segment 4 (carrying 5'-OH group or 5'-32P- or 33P-labeled phosphate group) in the presence of segment 3 followed by the joining of [5-32P]segment 5 in a second step. The duplex [I]' (segments 2 to 5) thus obtained was phosphorlated at the 5'-ends with polynucleotide kinase and then joined to segment 1 to give duplex [I] quantitatively. The preparative methods described have the desired flexibility for performing the subsequent operations necessary for the total synthesis of the structural gene for the tyrosine suppressor tRNA precursor.

Base Sequence↗
PubMed1978

Histochemical enzyme activity correlated to the structural segmentation of the proximal convoluted tubule in salt-depleted and salt-loaded rat kidneys.

In salt-depleted and salt-loaded rat kidneys a study was made of the structural segmentation of the proximal convoluted tubule (PCT) and the histochemical activity of non-specific acid and alkaline phosphatases and succinate dehydrogenase in the same segments. No quantitative structural or segmental alterations were observed, but significant changes in enzyme activity occured. These comprised: 1) A decrease in activity of acid phosphatase in segment 1 and the transitional zone in salt-depleted kidneys, and an increase in enzyme activity in segment 2 in salt-loaded kidneys. 2) a decrease in alkaline phosphatase activity in segment 2 in both salt-depleted and salt-loaded kidneys and 3) a decrease in succinate dehydrogenase activity in segment 2 in salt-depleted kidneys, and an increase in activity in the same segment in salt-loaded kidneys. Thus long-term variation in sodium intake are followed by segment-correlated variations in the activity of acid and alkaline phosphatase and succinate dehydrogenase in the PCT.

Acid Phosphatase↗
PubMed1979

Auxotonic contractions in cardiac muscle segments.

The dynamics of segment shortening have been measured in the central regions of isolated papillary muscles during muscle isometric and after-loaded isotonic contractions. Segment lengths are inferred from muscle cross-sectional area using an assumption that the segments remain isovolumic. Area is assessed with a magnetic induction technique. Infused microspheres have been used as visual markers to corroborate the segment length measurement. The results confirm the existence of major segmental shortening during muscle isometric conditions. However, the time course of shortening is not the same as that of force development. Rather, the segments remain shortened until after force has fallen significantly from its peak value. This behavior appears in the force-segment length plane as counterclockwise loops. The relationship of peak force to segment length has been determined and found to depend on the mechanical conditions under which the muscle is equilibrated. These results demonstrate the utility of the new technique and indicate central segment behavior that is substantially different from that observed for the whole muscle.

Animals↗
PubMed1979

The specification of metameric order in the insect Callosobruchus maculatus Fabr. (Coleoptera). I. Incomplete segment patterns can result from constriction-induced cytological damage to the egg.

Eggs of the pea-beetle Callosobruchus were divided into two at different stages of development. Both fragments were allowed to develop into partial larvae. The segment patterns of normal and partial larvae are described using cuticular markers of cell differentiation. To study the contribution of cytological damage to the segment gap phenomenon three different types of constriction were performed: complete and incomplete permanent constriction and complete temporary constriction. Changes in the structure of the egg can produce absence of segments resulting from two different effects. First, partial absence of segments results from a decreased egg circumference in the constriction region and involves the disturbance of a morphogenetic process (dorsal closure). Secondly, cytological damage can result in a gap between two arrays of segments. The loss of segments in the gap occurred in two different ways. In a spatial segment gap the two arrays of segments were physically discontinuous, whereas in a non-spatial gap the segments bordering the gap were juxtaposed in a physically continuous cuticle. The extent to which the gap phenomenon can be attributed to cytological damage is discussed. We also discuss, on the basis of certain dorsal defects, a possible stepwise specification of the dorsal transverse cuticular pattern.

Animals↗
PubMed1978

Focal segmental sclerosis or scarred focal proliferative glomerulonephritis?

We have made a blind retrospective analysis of 334 renal biopsies, each containing more than 10 glomeruli, from adults and children with glomerulonephritis, in order to assess the clinicopathological significance of segmental lesions. These were defined as endocapillary proliferation and/or sclerosis involving capillary loops, and a less than half the glomerular tufts. On optical microscopy of paraffin-embedded material, 57 biopsies containing segmental lesions were independently classified by two observes as "focal proliferative glomerulonephritis" or "focal segmental glomerulosclerosis". These results were then reviewed with immunofluorescence, electron microscopic and clinical data and an "executive" diagnosis reached. Scarred focal proliferative glomerulonephritis could not be reliably distinguished from focal segmental glomerulosclerosis by optical microscopy alone. Some cases of focal proliferative glomerulonephritis are not associated with systemic disease and may have negative immunofluorescence findings, and we were unable to distinguish scarring in these patients from the lesion of focal segmental glomerulosclerosis with any of the tools at our disposal. Some patients with scarred focal proliferative glomerulonephritis showed profuse proteinuria, a nephrotic syndrome and progression to renal insufficiency. These cases cannot therefore be differentiated from focal segmental glomerulosclerosis by their clinical features. It would seem that the morphological lesion of focal segmental glomerulosclerosis should be regarded as focal segmental glomerular scarring from a variety of insults, rather than a distinct disease entity.

Adolescent↗
PubMed1978

The outer segments of photoreceptive pinealocytes in the pineal organ of the funa, Carassius gibelio langsdorfi. A scanning electron microscopic study.

The form and size of the outer segments of photoreceptive pinealocytes in the pineal organ of the funa, Carassius gibelio langsdorfi, were observed with the scanning electron microscope. The height of the outer segments measures between 1 and 3 micrometer and the diameter varies widely from 1.5 to 8 micrometer. Various forms of outer segments, i.e. a slender type, a dome-like type, a cap-like type and a helical type, were demonstrated. The parallel-oriented filamentous processes of the inner segments have the same length as the outer segments and a diameter of approximately 100 nm; they are projections from the apical border of the inner segment and surround the cone-like outer segments. The processes make a right angle with the lamellar disks. The distance between two processes averages 100 nm. The lamellar disks of the outer segments are oriented at right angles to the modified cilium in the basal part, but the angle often changes in the peripheral part, where the lamellar disks are raised and become parallel to the cilium.

Animals↗
PubMed1977

Stationary microperfusion study of phosphate reabsorption in proximal and distal nephron segments.

Micropuncture studies demonstrate phosphate reabsorption in proximal tubules and between the late proximal and early distal convoluted tubule accessible to micropuncture. To further define the sites of phosphate reabsorption, the stationary microperfusion technique was applied to proximal and distal nephron segments. Phosphate reabsorption was evaluated in superficial loops of proximal tubules, descending segments beyound late proximal tubules accessible to micropuncture, ascending segments up to the point of micropuncture in the distal tubule, and superficial loops of distal tubules of thyroparathyroidectomized rats. Microperfusates of 1.3 or 2.6 nl (100 mmol/1 mannitol, 100 mmol/l NaCL, 32P-phosphate and 3H-inulin) were injected and then withdrawn after contact times of 2--108 s. Phosphate recovery relative to that of inulin was determined. A steep exponential decline of phosphate recovery (R) iwth increasing contact time (t) was observed in the superficial proximal tubule and descending segments. The slopes of the logarithmic regressions (10log R)/t, +/- SEM) were: -1.68 +/- 0.33 and -1.21 +/- 0.24min-1 in superficial proximal tubules and descending segments respectively. In contrast, no significant decline in phosphate recoveries (-0.02 +/- 0.04 and + 0.11 +/- 0.10 min-1) was apparent in the ascending segments and distal tubule. It is concluded that phosphate is reabsorbed in the proximal convoluted tubule and adjacent descending segments of the superficial nephron and that there is no significant phosphate reabsorption in distal convoluted tubules and adjacent ascending segments.

Animals↗
PubMed1979

Effects of digitalis on normal and abnormal left ventricular segmental dynamics.

To study the effects of digoxin on regional left ventricular performance, continuous ventricular dynamics were assessed in nine patients with stable coronary disease. Computer-assisted analysis of the fluoroscopic motion of surgically implanted mid wall myocardial markers was used. The markers define six minor ventricular radii and outline the left ventricle. One and one-half hours after administration of 1 mg of intravenous digoxin, mean velocity of circumferential fiber shortening for all segments increased 19 percent, from 0.67 +/- 0.06 to 0.78 +/- 0.06 circumference/sec (P less than 0.01) and ejection fraction increased 4.5 percent, from 0.50 +/- 0.03 to 0.53 +/- 0.03 (P less than 0.05). Segmental velocity of circumferential fiber shortening, total segmental shortening and early segmental systolic shrtening increased in 83 percent to 91 percent of normal segments, depending on which index was used. Only 45 to 55 percent of initially abnormal segments benefited from digoxin. In general, segmental dyssynergy increased even when net ventricular function was enhanced. These results suggest that in pateints with chronic left ventricular contraction abnormalities due to coronary disease, deterioration of performance in abnormal regions after administration of digoxin may result from increased stress imposed by increased afterload and by improved segmental dynamics in more normal areas.

Adult↗
PubMed1978

Segment stroke work and metabolism depend on coronary blood flow in the pig.

We determined the mechanical and metabolic effects of graded myocardial ischemia in 23 open-chest, anesthetized pigs. By connecting the midportion of the left anterior descending artery (LAD) to the carotid artery via a constant volume, calibrated pump, we reduced the flow in the LAD to 0, 25, 50, and 75% of control rates for periods of 1 h. Flows of 100% and 150% were also examined. Using pairs of ultrasonic crystals to measure segment dimensions, we calculated segment shortening and thickening, and total and systolic stroke work in the ischemic and normally perfused segments. Blood gases, pH, and lactate and inosine balances were determined from the regional coronary venous blood. At coronary blood flows of 0, 25, 50, and 75% of normal resting flow, total segment work was 8 +/- 8, 25 +/- 4, 51 +/- 5, and 80 +/- 6% of control, respectively, while systolic segment work was -2 +/- 5, -10 +/- 5, 40 +/- 5, and 86 +/- 7% of control, respectively (means +/- SE). Thus, the decrease in total segment stroke work is proportional to the decrease in flow over the range 0-100%. However, no useful work (i.e., systolic work) is done until flow exceeds 25%. Segment shortening and thickening are significantly depressed with flows diminished by only 25%. Segmental inosine production correlates with lactate production and parallels decreased mechanical performance.

Animals↗
PubMed1979

Innervation of the canine inferior vena cava. Distribution of adrenergic and cholinergic excitatory fibers among the embryologically distinct segments.

The innervation of three embryologically distinct segments of the canine inferior vena cava was investigated. These segments were termed A (supradiaphragm), B-C (intrahepatic and that between liver and renal veins), and D (infrarenal). Strips were cut from these segments, and their isometric tensions were recorded. Transmural electrical stimulation induced contractile responses in circular strips from segment B-C (66.5% of the maximum norepinephrine-induced response) and in those from D (14.4%), but not in A. These responses almost completely disappeared in the presence of phenoxybenzamine. In segment B-C, however, the remaining small contraction was markedly enhanced by neostigmine and abolished by atropine. The same phenomenon was also observed in the contraction remaining after reserpinization. Longitudinal strips from segment C responded similarly. Concentration-response curves of circular strips for acetylcholine were shifted by neostigmine markedly to the left only in segment B-C, while no significant shift occurred in A and D. It was concluded that the adrenergic innervation is remarkably dense in B-C, sparse in D, and probably lacking in A. In addition, a cholinergic excitatory innervation is present in segment B-C.

Acetylcholine↗
PubMed1978

[Reciprocal homology of the preotic mesodermal segments of representatives of different classes of vertebrates].

The data of the literature and those of the author on the origin of preotic mesodermal segments are discussed. Only in Cyclostomata all preotic segments are formed from the wall of archenteron and are larval segments. In all the gnathos tomata, the primary gastral segments are substituted, to different degrees, by postlarval peristonal mesoderm. The preotic mesomeres of Cyclostomata are homologous to II--IV mesomeres of Branchiostoma lanceolata. The anterior cephalic cavity and the premandibular segment of the elasmobranchia are homologous to I and II segments of Branchiostoma lanceolata. The mandibular mesoderm of the elasmobranchia includes the gastral mesoderm (homologous to III and some subsequent segments of Brachiostoma lanceolata) and peristomal mesoderm. The mandibular mesoderm in higher vertebrates has the same composition, but their anterior larval segments disappear and are substituted by gastral part of the mandibular mesoderm.

Amphibians↗
PubMedDate not supplied

Error measures for objective assessment of scene segmentation algorithms.

Scene segmentation is an important element in pattern recognition problems. Previous efforts to evaluate and compare scene segmentation procedures have been largely subjective. Quantitative error measures would facilitate objective comparison of scene segmentation algorithms. A theoretical discussion leading to a new generalized quantitative error measure, G2, based on comparison of both pixel class proportions and spatial distributions of "true" and test segmentations, is presented. This error measure was tested on 14 manual segmentations and 40 gynecologic cytology specimens segmented with five different scene segmentation techniques. Results indicate that G2 seems to have the desirable properties of correlation with human observation, categorization of error allowing for weighting, invariance with picture size and ease of computation necessary for a useful scene segmentation error measure.

Autoanalysis↗
PubMed1979

Segmental innervation of the chick forelimb following embryonic manipulation.

A number of studies have shown that the segmental innervation of some muscles in the developing limb undergoes some modification during the earliest stages of ontogeny. These observations can be interpreted in support of the hypothesis that the motor axons and muscles are matched during this period of development. As a further test of this suggestion we have made a quantitative examination of the motor innervation of the chick forelimb under conditions of controlled abnormal development. Embryos were surgically manipulated at stages before the motor axons invade the limb. The operations were controlled such that forelimbs were induced with segments deleted or reduplicated or simply that a segment of the spinal cord had been deleted. In preparations with abnormal limbs the motor innervation of the muscles present was the same as for those muscles in the normal limb. Where a spinal segment had been deleted the limbs developed normally and their innervation was completed by the remaining brachial segments. These results suggest that any particular matching property of a developing muscle does not develop as a consequence of its position in the limb relative to those segments of the limb proximal to it. Furthermore, that some muscles which are normally innervated by two spinal segments can be completely innervated by one of those spinal segments, in the absence of the other, suggests that any matching between growing axons and developing muscle cells is hierarchical rather than strictly all-or-nothing.

Animals↗
PubMed1979

Photoreceptor outer segment development: light and dark regulate the rate of membrane addition and loss.

The rate of membrane addition during outer segment development and the onset of membrane loss through shedding was evaluated for Xenopus laevis embryos reared at 23 degrees C in constant light (LL), constant darkness (DD), and cyclic light (12 hr L/12 hr D; LD). Embryos were placed under these lighting conditions 1 day following fertilization at open neural plate stages and were sampled each day for 9 days. Rod and cone outer segments were present in each treatment group on day 3 of development. At the end of 10 days of development, rod outer segment volumes were 708 +/- 195, 380 +/- 40, and 297 +/- 33 micrometer3 (mean +/- S.D.) for LL, LD, and DD treatment groups, respectively, whereas mean cone outer segment volumes were 57 +/- 8, 48 +/- 8, and 35 +/- 9 micrometer3 for these same treatment groups. The loss of outer segment material through shedding was assessed by monitoring the phagosome content of the pigment epithelium. Phagosomes were present in the pigment epithelium in DD embryos as early as 6 days of development, were present at day 5 only after the onset of the light cycle in LD embryos, and were rarely observed in LL embryos. The rate of outer segment membrane elaboration in rods (determined with 3H-leucine autoradiography) was virtually identical in LL and LD (100 and 98 micrometer3/day) but was greatly reduced in DD (70 micrometer3/day). These findings indicate that the relatively rapid rate of rod outer segment volume accumulation in LL embryos is due to a reduction in membrane loss through shedding and not to a higher rate of membrane addition as compared to animals reared in LD. In contrast, the reduced rate of rod outer segment development in DD embryos is the result of both a slower rate of membrane elaboration accompanied by the early onset and enhanced rate of membrane loss through shedding in darkness.

Animals↗
PubMed1976

Total synthesis of the structural gene for the precursor of a tyrosine suppressor transfer RNA from Escherichia coli. 8. Enzymatic joining of the chemically synthesized segments to form DNA duplexes corresponding to nucleotide sequences 23-60 and 23-66.

Polynucleotide ligase-catalyzed joining of the eight chemically synthesized deoxyribopolynucleotide segments (Fig. 1) comprising the nucleotide sequence 23-66 of the DNA corresponding to the Escherichia coli tyrosine tRNA precursor has been systematically investigated. Joining was studied using all possible combinations of 3, 4, and 5 and larger numbers of segments at a time. The extent of joining varied widely (0 to about 90%) in three component systems. The "self-structure" of some of the components evidently inhibited the joining. Addition of a fourth segment in general enhanced the extent of joining and optimal yields were obtained in systems containing six or more segments. A comparison of the T4-induced ligase and the E. coli polynucleotide ligase for joining of the chemically synthesized segments showed the E. coli enzyme to be inferior to the T4-induced ligase. Satisfactory syntheses of the duplexes [IIa] and [IIb] comprising, respectively, eight and seven segments were achieved in single steps. Of the two terminal segments carrying 5'-OH groups in the duplexes, only one (segment 7) was used in the prephosphorylated form. The duplexes were isolated pure and characterized by enzymatic degradations and by electrophoresis.

Base Sequence↗
PubMed1978

Masses, centers-of-gravity, and moments-of-inertia of the body segments of the rhesus monkey (Macaca mulatta).

Segmental parameters (mass, center-of-gravity, and moment-of-inertia) are necessary for biomechanical analyses of a species' locomotor behavior. Seven male and eight female adult rhesus monkey cadavers were dismembered in order to determine segmental parameters. Mean values for the segment masses and moments-of-inertia are presented for males and females, separately and together. Statistical tests revealed significant differences between the sexes for these parameters. Regression equations for predicting segment masses and moments-on-inertia were developed for the sexes separately and pooled. For most segments the male and female equations did not differ significantly in slope or y-intercept. The center-of-gravity for each segment is presented as a mean percentage of the distance between the proximal and distal joint centers. The regression equations and center-of-gravity locations presented here permit biomechanical investigations of rhesus monkey locomotion without the necessity of subsequent sacrifice. The segmental parameter values determined for the rhesus monkey are compared with available data for other primate and mammalian species and the biomechanical and adaptive implications of such comparisons are discussed.

Animals↗
PubMed1977

Segmental dearterialization in penetrating renal trauma.

Refractory renal haemorrhage following low velocity penetrating trauma has conventionally been treated by nephrectomy or partial nephrectomy. Anatomical studies have demonstrated that the renal artery branches are end-arteries, each branch supplying a renal segment, with no collateral artery supply between segments. Life-threatening haemorrhage is arterial, and usually issues from a single segmental artery easily demonstrable by renal angiography. Fourteen patients had various segmental arteries ligated to control haemorrhage. Associated visceral injuries were present in 4 patients. Preoperative selective renal arteriography was possible in 13 patients and demonstrated the bleeding site in all cases. Segmental dearterialization produced haemostasis in 12 of the 14 patients. One patient required nephrectomy and one patient ligation of a second segmental artery to control bleeding. All the patients survived the operative procedure. Supine renin levels were normal on the fourteenth postoperative day and no patient developed hypertension during the follow-up period of 9-24 months. Segmental renal dearterialization by open operation is a simple and effective technique of controlling refractory renal haemorrhage with maximum preservation of renal parenchyma.

Adolescent↗