Capillary Space Research Articles

Quantitative assessment of the rat stria vascularis

Stria vascularis tissues from standardized regions in the basal, middle and apical turns of the rat cochlear duct were assessed quantitatively. Strial width, number of marginal cells across the strial width, radial area, as well as the volume density of the different components of the stria vascularis were determined for each standardized region. Strial width, number of marginal cells across the strial width and the radial area were greatest in the basal region and least in the apical region of the cochlea. The volume density of intermediate cells and capillary space was statistically unchanged in the three examined regions of the stria vascularis. However, the volume density of marginal cells and that of basal cells were different between regions. The volume density of marginal cells was highest in the basal turn while the volume density of basal cells was greatest in the apical turn. An objective assessment of the response of the stria vascularis to environmental conditions can be made by kant of its cellular architecture, providing a means to compare the effects of various agents between animal models used to study human inner ear dysfunction.

Physicochemical properties of commercially available mouthrinses

This study evaluated physicochemical properties of eight commercially available mouthrinses, namely surface tension, in vivo enamel contact angle, viscosity, penetration coefficient, acidity and buffer capacity. The penetration coefficient, determined by the surface tension, contact angle and viscosity, is a measure of the ability of a liquid to penetrate into a capillary space, such as interproximal regions, gingival pockets and pores. The acidity is often determined by a compromise of the requirements for taste, enamel remineralization and stability of the solution. Among the eight mouthrinses evaluated, the physicochemical properties differed greatly, in particular, the penetration coefficient which varied by a factor of 1.8 over the products tested. Surprisingly several of the products tested were found to be extremely acidic.

Morbidity and survival patterns in patients after radical hysterectomy and postoperative adjuvant pelvic radiotherapy

Morbidity and survival patterns were reviewed in 50 patients who underwent radical hysterectomy, pelvic lymphadenectomy, and adjuvant postoperative pelvic radiotherapy for invasive cervical cancer. Ninety percent of the patients were FIGO stage IB, and 10% were clinical stage IIA or IIB. Indications for adjuvant radiotherapy included pelvic lymph node metastasis, large volume, deep stromal penetration, lower uterine segment involvement, or capillary space involvement. Seventy-two percent of the patients had multiple high-risk factors. An average of 4700 cGy of whole-pelvis radiotherapy was administered. Ten percent of the patients suffered major gastrointestinal complications, 14% minor gastrointestinal morbidity, 12% minor genitourinary complications, one patient a lymphocyst, and one patient lymphed-ema. Of the five patients with major gastrointestinal morbidity, all occurred within 12 months of treatment. Three patients required intestinal bypass surgery for distal ileal obstructions and all are currently doing well and free of disease. All of the patients who developed recurrent disease had multiple, high-risk factors. The median time of recurrence was 12 months. All patients recurred within the radiated field. Actuarial survival was 90% and disease-free survival 87% at 70 months. It is our opinion that the morbidity of postoperative pelvic radiotherapy is acceptable, and benefit may be gained in such a high-risk patient population.

Small vessel phenomena in the coronary microcirculation: Phasic intramyocardial perfusion and coronary microvascular dynamics

To place the characteristics of the coronary microcirculation in perspective to another muscular organ system, we have compared various parameters from exchange vessels in the heart and red skeletal muscle (Table 1). The major differences between cardiac and skeletal muscle microcirculations relate to the larger density of capillaries in the heart. This increased density is responsible primarily for a greater capillary filtration coefficient-permeability-surface area product to various solutes, surface area, and decreased intercapillary distance. These features most likely represent an adaptation of the microcirculation of the heart to the very high, continual metabolic demands. Interestingly, capillary permeabilities and reflection coefficients of different solutes are in the same range (although the heart tends to have higher capillary permeabilities). Thus, the adaptation of the coronary circulation to facilitate exchange of nutrients and solutes is mediated via an increase in the numbers of exchange vessels, rather than modifications of the membrane characteristics of these exchange vessels. Within the last decade, there has been much information assimilated on the regulation of the coronary microcirculation. Most of the knowledge has been the result of many indirect approaches to studying the coronary microcirculation (indicator-dilution techniques, nuclidelabeled microspheres, plasma-lymph concentration of solutes). There are relatively few direct observations on regulation of the coronary microcirculation. This is primarily due to difficulties in techniques. Exploration of the phasic nature of intramyocardial perfusion is handicapped by the location of these intramuscular vessels. Visualization of the coronary microcirculation is hampered by movements of the heart, and such measurements are restricted to the superficial layers of the myocardium. It is worth emphasizing that direct observations of red cell velocities in epicardial capillaries, measurements of microvascular caliber, and the pressure profiles in the coronary microcirculation are restricted to the superficial, epicardial layer. It is not unreasonable to speculate that microvascular events and regulation occurring in the subepicardium may be quite different than that in the subendocardium. There are several salient points in this review that are worth emphasizing. First, measurements of phasic blood flow in an epicardial coronary artery do not accurately predict the phasic nature of intramyocardial perfusion. Observed differences between the phasic nature of epicardial blood flow and that in intramyocardial blood vessels is due to epicardial capacitance, which can be modulated by distending pressures and vasomotor tone. Second, extravascular compressive forces markedly influence the phasic nature of intramyocardial blood flow. Augmenting such forces augments systolic-negative blood flow. Third, spatial and temporal heterogeneity of myocardial perfusion occurs in the normal myocardium (with the vasomotor tone intact). Heterogeneity of perfusion is due to twinkling of precapillary sphincters that regulate flow to individual capillary fields. Fourth, the capillary bed of the myocardium is composed of endothelium, which has similar permeability characteristics to most other organ systems in the body (notable exceptions are the brain, with very low permeability, and the liver, with very high permeability). There is, however, a tremendous potential for the filtration of water and solutes from the capillary space to the vascular space due to the very large surface area of the capillary bed, which is much larger than most other organ systems. Fifth, in contrast to many other organ systems, the coronary circulation is characterized by a fairly substantial proportion of total coronary resistance residing in relatively large microvessels (40% to 45% of total coronary resistance is proximal to 100 μm arterioles). Furthermore, this resistance is due primarily to active vasomotor tone rather than structural features of the coronary vasculature system. Direct studies of the coronary microcirculation are yet in the embryonic stages. There are still substantial technical problems that have not been solved. For instance, there are still no measurements of capillary pressures in the heating heart or of microvascular dynamics in subendocardial vessels. Undoubtedly, there should be efforts directed toward development of techniques to enable such measurements. Such endeavors will require the cooperation of physiologists, engineers, computer scientists, and cardiologists to solve these seemingly insurmountable problems.

A strong correlation between glomerular filtration rate and filtration surface in diabetic nephropathy.

Quantitative structural studies were performed in kidney biopsy specimens from 24 long-term Type 1 (insulin-dependent) diabetic patients with persistent albuminuria due to diabetic glomerulopathy. Ten patients were receiving antihypertensive treatment, and among the remaining patients the mean blood pressure was 142/91 mm Hg (SD = 11/9). The urinary albumin excretion rate showed a range from 100 to 5494 micrograms/min (geometric mean 688 micrograms/min.) Glomerular filtration rate also showed a wide range, from supranormal to markedly decreased values (128 to 28 ml.min-1. (1.73 m2)-1, mean 75). The filtration surface (interface between capillary and urinary space) per total number of nephrons (open + occluded) was estimated by combined light-and electron microscopy. The percentage occluded glomeruli as well as structural quantities in the open glomeruli were taken into account in this estimate. A highly significant correlation was seen between glomerular filtration rate and filtration surface per nephron (r = 0.77, p less than 10(-4). The percentage occluded glomeruli contributed significantly to the variation in glomerular filtration rate (for this relationship tested separately r = -0.78, p less than 10(-5). The volume of open glomeruli was even larger than that seen in early diabetic glomerular hypertrophy and tended to increase with the percentage of glomerular closure, indicating that a compensatory hypertrophy might have taken place. In the open glomeruli the filtration surface constituted a smaller percent of total capillary surface (the remaining part facing the mesangial regions) than in early diabetic patients and control subjects. Our study has demonstrated that reduced glomerular filtration surface is closely associated with reduced glomerular filtration rate in Type 1 diabetic patients with diabetic nephropathy.

An electron microscope study of kidney basement membrane changes in the mouse by lipoteichoic acid from Streptococcus pyogenes

Mice injected repeatedly, intraperitoneally or intravenously, for approximately 1 month with a total of 1.04 mg lipoteichoic acid from a nephritogenic strain of Streptococcus pyogenes lost weight. Analysis by electron microscopy revealed that they also exhibited extensive kidney changes in basement membrane morphology which resembled, in part, those observed in human poststreptococcal glomerulonephritis. For example, the glomerular basement membrane became electron dense and exhibited at least a twofold increase in width sporadically within the same preparation after exposure to lipoteichoic acid. Also, whereas appreciable loss or reduction in epithelial foot processes as a result of fusion was clearly evident, epithelial slits and slit membranes or diaphragms between normal foot processes were not selectively affected. In addition, another mostly thickened, highly coiled or serpentinelike basement membrane with amorphous nodules appeared in these preparations. This type membrane was not observed surrounding the capillary lumina and was the most pronounced abnormality apparent in almost all preparations from mice exposed to lipoteichoic acid. Likewise, the proximal tubular basement membrane became variable in width and increased in electron density in mice given lipoteichoic acid as compared with controls. In addition, this membrane was often punctuated with various morphological protrusions originating from only its thickened areas and which extended away from, and not into, the capillary space. This change was only associated with the basement membrane of the proximal tubular capillaries. All membrane changes persisted but gradually subsided, with normal kidney membrane morphology reappearing on the 4th day following the last injection of lipoteichoic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the anaphylatoxin, C5a, on renal and glomerular hemodynamics in the rat

The effects of intrarenal infusion of the complement-derived anaphylatoxin, C5a, upon glomerular hemodynamics were examined in the Munich-Wistar rat, a strain with glomeruli on the kidney surface. Human C5a (1.5 micrograms/min) or vehicle was infused into the left renal artery for 12 min, and glomerular capillary (PG) and Bowman's space pressures, nephron plasma flow (SNPF) afferent and efferent arteriolar protein concentrations, nephron filtration rate (SNGFR) and the glomerular ultrafiltration coefficient (LpA) determined. Human C5a infusion resulted in a reduction in SNPF due to increased efferent arteriolar resistance, and PG increased which maintained SNGFR constant. LpA was numerically lower but not significantly decreased. Infusion of porcine C5ades Arg decreased glomerular filtration rate and renal blood flow. No polymorphonuclear leukocytes were observed within glomerular capillaries of C5a infused rats, and rat leukocytes did not exhibit receptors for human C5a infused. Renal artery infusion of either human C5a or porcine C5a resulted in renal hemodynamic alterations and, as documented for human C5a, effects of C5a upon renal vascular resistance can be added to the known effect of C5a on the polymorphonuclear leukocyte.

Oxygen free-radical reduction of brain capillary rubidium uptake.

Free radicals are proposed to play a role in the injury following cerebral ischemia in which cerebral edema is a prominent feature. To determine whether free radicals might alter the movement of ions and water across the blood-brain barrier, we examined their effect on brain capillary transport. Rat brain capillaries were isolated, incubated with a system that generates free radicals, and various capillary transport systems were studied. Rubidium uptake was reduced 74% whereas rubidium efflux, glucose transport, and capillary water space were unchanged. The results following the addition of radical scavengers indicated that hydrogen peroxide or a related free radical was the toxic species. These data suggest that free radicals can impair capillary endothelial cell mechanisms that help maintain homeostasis of electrolytes and water in brain.

Formation of Ice on Several Substrates

The hexagonal ice formation on the surfaces of several substrates which have different crystallographic configuration of oxygen atoms from that on the preferentially crystallized surface of ice was studied by taking rate and direction of cooling into consideration. It was found that the cooling direction is the dominating factor for the preferential orientation of crystal axis of ice formed on a substrate. That is, the hexagonal ice grows preferentially along c-axis for thin layer ice and along c-axis or a-axis for fine columnar ice parallel to the cooling direction, regardless of the degree of epitaxy of oxygen atoms on surfaces between substrate and ice, or of the degree of wettability between substrate and water. But it has been also found that the freezing temperature lowering and the temperature range for single crystal formation of ice in the whole capillary space of glass tubing on substrates were significantly influenced by the epitaxy, i.e. the degree of misfit of interatomic spacing of oxygen on crystallographic surfaces of substrate and ice (00l).

Morphometric changes of the lung induced by inhaled bacterial endotoxin

Due to the ubiquitous nature of airborne endotoxin, an understanding of pulmonary alterations which follow inhalation of environmentally realistic concentrations of purified bacterial derived lipopolysaccharide (LPS) is important. Using LPS derived from Enterobacter agglomerans, a bacterium found in cotton and cotton mill dust, aqueous aerosols (effective LPS concentration 4 μg/m 3) were generated and used to expose either normal hamsters ( N = 6) or those rendered endotoxin tolerant by pre-ip injection of 0.1 LD 50 LPS. Control groups (normal— N = 6; tolerant— N = 6) received saline aerosol only. At 6 hr after 5-hr aerosol exposure, lungs of all animals were fixed, processed for light and transmission electron microscopy, and subjected to qualitative and to multitiered morphometric analysis using standard point counting techniques. Qualitative evaluation of TEM micrographs from LPS aerosolized-nontolerant hamsters showed endothelial alteration (focal disruption, subendothelial space formation, and cytoplasmic blebbing) but volume and number of endothelial cells were not changed indicating only slight, focal endothelial damage. Quantitatively, septal capillary blood space in nontolerant, LPS aerosolized hamsters showed increased V v of PMNs and platelets. These changes were not seen in tolerant induced-LPS aerosolized hamsters. Independent of tolerization treatment, LPS inhalation led to a decrease in fixed lung volume and an increase in numerical density of endothelial pinocytotic vesicles. It is concluded that the inhalation of realistic, environmental levels of bacterial endotoxin may induce significant changes in distal lung and may be important in the pathogenesis of byssinosis and adult respiratory distress syndrome.

Growth of Ficus benjamina in Combinations of Peat, Sand, and Melaleuca

Abstract Ficus benjamina were grown in potting media containing various combinations of Florida sedge peat, builder’s sand, and shredded portions of Melaleuca quinquenervia (Cav.) S.T. Blake and irrigated either 2 or 4 times per week. Eight months after initiation of experiment, plants were sleeved and placed in dark coolers maintained at 13° ± 1°C and 85% ± 10% RH for 4 weeks. After removal from coolers, plants were placed in rooms with irradiance of 15 μmol s-1m-2, temperature of 25° ± 2° and 60% ± 10% RH. Plant height was not affected by treatment. Plant grade, fresh weight and root grade decreased with an increase in shredded Melaleuca bark and wood. Plants watered 2 times/week had less than one-half the leaf drop of plants watered 4 times/week. As the percentage of shredded Melaleuca bark and wood decreased, pH and the percentage of noncapillary pore space decreased, and soluble salts and capillary pore space increased. An increase in sand increased pH, soluble salts, bulk density, and decreased cation exchange capacity and percent capillary pore space.

Glomerular ultrafiltration dynamics during increased renal venous pressure.

The effects of unilateral partial renal venous ligation on whole kidney and single nephron function were determined in anesthetized euvolemic Munich-Wistar rats using clearance, blood flow, and micropuncture techniques. Increased venous pressure (4-22 mmHg) reduced glomerular filtration rate (GFR) and renal plasma flow (RPF) to 60% of control values; filtration fraction (FF) was constant. Similar responses occurred in the superficial cortex, as evidenced by a 40% fall in SNGFR determined while intratubular pressure was maintained at the elevated precollection level. Fractional reabsorption by the proximal convoluted tubule remained constant, indicating maintenance of glomerulotubular balance. The contralateral kidney exhibit a diuresis and natriuresis while GFR and RPF were stable. In the experimental kidney single nephron glomerular plasma flow decreased by 35% due to increments in preglomerular and efferent arteriolar resistance. The transcapillary hydrostatic pressure gradient was unchanged since there were similar 7- to 8-mmHg increases in glomerular capillary and Bowman's space pressures. Filtration pressure disequilibrium was observed in control and experimental periods. Mean effective ultrafiltration pressure was similar in both periods. Specific values for the ultrafiltration coefficient (Kf) fell from 0.023 to 0.015 nl . s-1. mmHg-1. Accordingly, partial renal venous ligation produces ipsilateral vasoconstriction and a fall in GFR that is primarily due to a proportional decline in Kf.

Light- and electron-microscopic immunocytochemistry of glutamic acid decarboxylase (GAD) in the basal hypothalamus: Morphological evidence for neuroendocrine γ -aminobutyrate (GABA)

GABAergic cells and axon terminals were localized in the basal hypothalamus of different species (rat, mouse and cat), by means of an immunocytochemical approach using a specific and well-characterized antiserum to the GABA biosynthetic enzyme, glutamate decarboxylase. Lightmicroscopic visualization was performed with an indirect immunofluorescence method and electron-microscopic observations were made on material with pre-embedding staining and use of the peroxidase-antiperoxidase procedure. At the light-microscopic level, a dense immunofluorescent plexus was observed over both the medial and lateral parts of the external layer of the median eminence. The labelling extended from the rostral part of the median eminence up to the pituitary stalk. Over the subependymal and internal layers only a few immunoreactive dots were visible, except around the blood vessels where they appeared more concentrated. Immunoreactive varicosities could be found following the outlines of the capillary loops and lining tanycyte processes, especially in the median eminance midportion. At the electron-microscopic level, the immunolabelling was exclusively found over neuronal profiles in the median eminence. The latter represented a small fraction of the total number of varicosities visible on the same section. Labelled profiles typically contained numerous small clear synaptic vesicles and only a few or no dense-core vesicles. In the subependymal and internal layers, rare labelled endings were found close to ependymal cells or among transversally cut fibers, respectively. In the palisadic zone, elongated positive boutons were visible intermingled with bundles of unlabelled axons and glial or ependymal processes. In the neurohemal contact zone, immunoreactive endings were observed among unlabelled neurosecretory endings in close vicinity to fenestrated capillary perivascular space. Small moderately intense immunofluorescent varicosities were observed all over the hypothalamus. The density of the glutamate decarboxylase-positive network was higher than in most diencephalic regions. Intraventricular or topical injection of colchicine allowed the visualization of small lightly immunoreactive cells in the diffusion area of colchicine. In the arcuate nucleus labelled axonal endings containing small pleomorphic synaptic vesicles and sometimes a few dense-core vesicles were observed at the electron-microscopic level. Typical synaptic junctions were commonly found between positive endings and unlabelled perikarya, or more frequently, unlabelled dendrites. These findings show that glutamate decarboxylase-containing endings are localized in several strategic sites for potential GABAergic neuroendocrine regulations. The GABAergic endings found among neurosecretory endings in the neurohemal contact zone may provide the morphological support for the release of γ -aminobutyrate into the portal blood flow as an hypothalamic hypophysiotropic hormone. Alternatively, neurosecretory cells might be under GABAergic control expressed either at their terminal level within the median eminence or the cell body level within the parvicellular hypothalamic nuclei.

Mechanism of reduced glomerular filtration rate in chronic malnutrition.

To determine the physiological basis for the low glomerular filtration rate in chronic malnutrition, micropuncture studies were performed in Munich-Wistar rats chronically pair-fed isocaloric diets of either low (group 1, nine rats) or high protein content (group 2, nine rats). Despite the absence of hypoalbuminemia, average values for single nephron and total kidney glomerular filtration rate were nearly 35% lower in group 1 than in group 2. Mean values for glomerular capillary and Bowman's space hydraulic pressures were essentially identical in the two groups, thereby excluding glomerular transcapillary hydraulic pressure difference as the cause for the low filtration rates in group 1 animals. On the other hand, average glomerular capillary plasma flow rate and glomerular capillary ultrafiltration coefficient were significantly lower (by approximately 25 and approximately 50%, respectively) in group 1 than in group 2. The fall in glomerular capillary plasma flow rate was the consequence of increased afferent and efferent arteriolar resistances. Plasma and erythrocyte volumes were found to be equal in five additional pairs of group 1 and group 2 rats. Thus, the substantial alterations in the ultrafiltration coefficient, glomerular capillary plasma flow rate, and renal arteriolar resistances responsible for the low filtration rate in group 1 animals were not merely a consequence of decreased circulating blood or plasma volumes. Mean values for glomerular cross sectional area were significantly lower in group 1 than in group 2 despite similar values for kidney weight in the two groups. This reduction in glomerular cross sectional area in group 1 rats is presumed to reflect a decrease in effective filtration surface area and therefore likely accounts, at least in part, for the decline in ultrafiltration coefficient observed in this group.Finally, since the daily caloric intake of group 2 animals was restricted because of pair feeding requirements tied to the group 1 rats, we studied a third group of seven rats (group 3) allowed an ad lib. intake of the same high protein diet as given to group 2 rats. Average values for single nephron glomerular filtration rate and its determinants were found to be indistinguishable between groups 2 and 3. These results suggest that low protein intake, rather than calorie deficiency per se, is primarily responsible for the reduction in filtration rate seen in this experimental model of chronic malnutrition.

Effect of dihydrostreptomycin on cochlea of KK mouse (author's transl)

Using a phase contrast microscope and electron microscope, the effect of DHSM on the cochlea of KK mouse was studied. DHSM 200mg per kg of body weight was administrated daily, into the peritoneal space for 21 days.Same number of dd-strain mice were served as the control. No pathological finding was observed in the cellular element of stria vascularis, but a micro-embolism of destructed cell element was formed in the capillary space of KK mouse, but not of dd-strain mouse.It was suspected that these findings may be the initial stage of the degenerative process in the stria vascularis of KK mouse, and further the vascular vulnerability of this animal for the DHSM ototoxicity.

Effect of hydrostatic tensile stress on the growth of Escherichia coli and Bacillus cereus.

The specific growth rates of Escherichia coli and Bacillus cereus were measured for growth media in a flask, a lens-plate arrangement simulating an isolated capillary space, and a lens-plate arrangement under hydrostatic tensile stress. The specific growth rates of the bacteria were the same for the flask and lens-plate arrangement without hydrostatic tensile stress, but were enhanced when the growth media were subjected to hydrostatic tensile stress. The enhanced specific growth rates reached steady values at a tensile stress of 40 pascals. The effect was observed up to tensile stresses of around 100 pascals. The maximum increase in specific growth rate was 25% for E. coli and 22% for B. cereus.

1072 FACTORS LIMITING GLOMERULAR FILTRATION RATE IN THE IMMATURE RAT

In 14 immature (30-45 day) Munich-Wistar rats with surface glomeruli accessible to micropuncture, glomerular capillary (PGC) and Bowman's space (PT) hydraulic pressures, efferent arteriolar oncotic pressure (ΠE), single nephron (SN)GFR, initial glomerular plasma flow rate (QA), afferent (RA) and efferent (RE) arteriolar resistances, and glomerular capillary ultrafiltration coefficient (Kf) were determined under euvolemic conditions. Results are compared with those from 14 adult (70-100 day) rats studied under similar conditions. (Mean ± SE, † P <.01) Thus, mean values for PGC, PT and SNFF in immature were essentially the same as those in adult. Since the net force for ultrafiltration at the efferent end of the glomerular capillary network (given by PGC-PT-ΠE) was essentially zero in immature and adult alike, Kf was not a factor limiting SNGFR in either group. Instead, the lower values for SNGFR per gram kidney weight (KW) in immature than adult are primarily a consequence of lower QA/gKW, the latter due, at least in part, to markedly higher RA and RE. The causes for these higher resistances, whether structural or humoral, remains to be determined.

Angiotensin II effects upon the glomerular microcirculation and ultrafiltration coefficient of the rat.

The effects of both synthetic and biologically produced angiotensin II (AII) upon the process of glolerular filtration were examined in the plasma-expanded (2.5% body wt) Munich-Wistar rat, by micropuncture evaluation of pressures, nephron plasma flow (rpf) and filtration rate (sngfr). Plasma expansion was chosen as a control condition because (a) response to AII was uniform and predictable, (b) endogenous generation of AII was presumably suppressed, and (c) the high control values for rpf permitted accurate determination of values for the glomerular permeability coefficient (LpA) before and during AII infusion. With subpressor quantities of synthetic Asn-1, Val-5 AII (less than 5 ng/100 g body wt/min), sngfr fell from 47.7 in the control group to 39.8 nl/min/g kidney (P less than 0.005). The rpf fell to 60% of control values (P less than 0.001). Measurement of glomerular capillary (PG) and Bowman's space (Pt) hydrostatic pressures in surface glomeruli with a servo-nulling device permitted evaluation of the hydrostatic pressure gradient (deltaP = PG - Pi). DeltaP increased from 38.1 +/- 1.2 in control to 45.9 +/- 1.3 mm Hg after Asn-1, Val-5 AII and essentially neutralized the effect of decreased rpf in sngfr. The sngfr then fell as a result of a decreased in LpA from 0.063 +/- 0.008 in control to 0.028 +/- 0.004 nl/s/g kidney/mm Hg after Asn-1, Val-5 AII (P less than 0.02). Lower doses of Asp-1, Ile-5 AII (less than 3 ng/100 g body wt/min) had no effect on sngfr, rpf, deltaP, and afferent and efferent vascular resistance, but significantly elevated systemic blood pressure, suggesting peripheral effects on smooth muscle at this low dose. LpA was 0.044 +/- 0.007 nl/s/g kidney/mm Hg after low-dose Asp-1, Ile-5 AII, and 0.063 +/- 0.008 in the control group (0.02 greater than P greater than 0.1). Higher, equally pressor doses of native AII (5 ng/100 g body wt/min) produced effects almost identical to similar quantites of synthetic Asn-1, Val-5 AII upon rpf, deltaP, sngfr, and renal vascular resistance. LpA again fell to 0.026 +/- 0.004 nl/s/g kidney/mn Hg, a value almost identical to that after the synthetic AII. Paired studies with Asp-1, Ile-5 AII also demonstrated a consistent reduction in LpA.

Desert Termite1 Control in a Shortgrass Prairie: Effect on Soil Physical Properties2

Control of the desert termite Gnathamitermes tubiformans (Buckley) in a shortgrass prairie in W Texas resulted in an improvement in the watershed value and soil-water relationships for forage plants. The percentages of > 1-mm soil aggregates were greater on termite-free soils, whereas percentages of < 1-mm aggregates were greater on termiteinfested soils. Organic carbon, forb production, and litter accumulation increased significantly on termite-free soils. Capillary pore space was normally higher in termite-free soils, while non-capillary pore space was normally higher in termite-infested soils. Termite control had no effect on total pore space, hydraulic conductivity, and bulk density in the soil studied. Rainfall infiltration was greater on termite-free soils after the 1st 15 min of a simulated rainstorm. Runoff and sediment load were greater on termite-infested rangeland than on termite-free rangeland. Evapotranspiration was greater on termite-free soils during a 7-day period following rainfall application. However, termite-free soils retained more moisture during dry periods than termite-infested soils.

The cellular response of saurian pancreatic islets to chronic insulin administration

Moderately degranulated pancreatic A cells were observed by light, phase, and electron microscopy after chronic insulin administration in the lizard Anolis carolinensis. The reduced granularity of A cells is presumably due to glucagon release in response to insulin-induced hypoglycemia. Secretion of glucagon is compatible with the observed reduction in glycogen content of the hepatocytes. The ultrastructural observations made during the periods of maximal A cell degranulation suggest a new interpretation of glucagon secretion. The salient feature of the proposed secretory mechanism is intracytoplasmic release of glucagon. Other ultrastructural changes appear to be associated with the secretory process. The two most prominent changes were: pleomorphic A granule profiles often exhibiting knoblike protuberances, and short, basal infoldings of the A cell plasma membrane abutting the capillary space. The role these changes might have in the release of glucagon is discussed. A, B, and D cells were identified by light, phase, and electron microscopy. With the light microscope, A cells were stained by phosphotungstic acid-hematoxylin, and Ponceau-acid fuchsin. B cells were aldehyde fuchsin positive. D cells were argyrophilic. With the phase microscope, A cells contained large, dense secretory granules; B cells had the smallest secretory granules of the three major cell types; and D cells had large granules which were less dense than A granules. With the electron microscope, A granules tended to be oval in profile, were electron opaque with a predominantly homogeneous matrix, and had a long axis of 700 to 800 nm. B granules were round to oval in profile, had a moderately electron opaque matrix with a central dense core, and were approximately 450 nm in diameter. D granules were large, approximately 650 nm in diameter, round in profile and moderately electron opaque. The matrix of D granules was separated from the limiting membrane of the granule by a narrow, electron lucent space. Using the above criteria, the islet cell population contained approximately 50% A cells, about 40% B cells, and 10–15% D cells.