Biomedical subjects

J A Paterson

Publications and source records attributed to J A Paterson.

At least 37 records · Page 2Linked to original sources

PubMed1993

The effects of endophyte-infected tall fescue consumption and use of a dopamine antagonist on intake, digestibility, body temperature, and blood constituents in sheep.

Two experiments were conducted with lambs that consumed endophyte-infected (Acremonium coenophialum) tall fescue diets under elevated temperature and humidity and supplemented with the dopamine antagonist metoclopramide (M). In Exp. 1, 12 ruminally cannulated wethers (average weight 49 kg) were allotted by weight to either an endophyte-free diet (E-) or endophyte-infected diet (E+; 1,170 ppb of ergovaline), or E+ supplemented with M (15 mg/kg of lamb BW; E+M). Ad libitum DM intake and digestibility were lower (P < .05) for E+ than for E- diet. Supplementation of E+ with M increased (P < .05) DM intake by 27.6% but did not change DM digestibility. Body temperature increased (P < .05) when lambs consumed E+ and was further increased when M was supplemented. For Exp. 2, 19 wether lambs (average weight 24 kg) were allotted to treatments to evaluate the effects of endophyte consumption (0 vs 2,430 ppb of ergovaline) and supplementation with M (0 vs 20 mg/kg BW). An interaction (P < .05) of main effects was measured for DM intake. Lambs that consumed E+M consumed more DM than did lambs fed only E+, but lambs offered the E- diet and supplemented with M did not increase DM consumption. Diet DM digestibility was not different among treatments. Skin vaporization decreased (P < .05) due to E+ consumption and M supplementation. The concentration of prolactin in plasma was decreased (P < .05) by consumption of E+ (8 vs 136 ng/mL) and did not increase due to M supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acremonium↗

PubMed1993

The effects of endophyte-infected tall fescue consumption on diet utilization and thermal regulation in cattle.

Two experiments were conducted to determine the effects of endophyte fungus (Acremonium coenophialum) ingestion in tall fescue diets and environmental temperature on heat dissipation and diet utilization by cattle. In Exp. 1, 12 Angus heifers (average weight 244 kg) were allotted by weight to either an endophyte-free (E-) or endophyte-infected (E+; 381 ppb of ergovaline) diet. Environmental temperature varied between 22 and 32 degrees C. Voluntary DM and water intakes were similar (P > .10) among treatments. Rectal temperatures and concentrations of prolactin in plasma were lower (P < .05) after ingestion of the E+ diet. Plasma triiodothyronine, thyroxine, and cortisol concentrations were not affected by diet. In Exp. 2, 24 Holstein steers (average weight 114 kg) were allotted by weight to either E- or E+ (285 ppb of ergovaline) and one of two environmental temperatures (22 or 32 degrees C). At 32 degrees C, feed intake was reduced by 22%, and water consumption was increased by 62% compared with steers housed at 22 degrees C. Consumption of E+ reduced feed intake by 10% but did not influence water consumption. Plasma concentration of prolactin was decreased (P < .05) within 48 h after consumption of E+. Rectal temperatures increased in response to both environmental temperature (P < .05) and E+ consumption (P = .06). Digestibilities of DM and OM for E+ were 9% lower (P < .05) than for E-.(ABSTRACT TRUNCATED AT 250 WORDS)

Acremonium↗

PubMed1993

Combinations of starch and digestible fiber in supplements for steers consuming a low-quality bromegrass hay diet.

Five steers (690 kg) with ruminal and duodenal cannulas were fed 100% bromegrass hay or 60% bromegrass hay:40% concentrate at 90% of their ad libitum DMI. The concentrate consisted of ground corn (GC) and(or) soybean hulls (SBH): 1) 100% SBH; 2) 66% SBH/33% GC; 3) 33% SBH/66% GC; or 4) 100% GC. Increasing level of corn inclusion decreased (linear, P < .01) DM and OM digestion (corrected for microbial DM and OM flow) in the rumen. Neutral detergent fiber digestion decreased in the rumen (quadratic, P = .05) and total tract (linear, P = .06) with increasing level of corn. Ruminal NDF digestion (quadratic, P = .05) and duodenal microbial N flow (quadratic, P < .01) were greatest for 66% SBH/33% GC, whereas total N flow to the duodenum was similar (P > .10) among treatments. Microbial efficiency increased (quadratic, P = .10) as the level of corn inclusion increased. Molar percentage of ruminal acetate decreased (linear, P < .01) with increasing level of corn, whereas molar percentage of butyrate increased (linear, P < .10). Carboxymethylcellulase activity was greatest (quadratic, P = .08) for 66% SBH/33% GC and paralleled NDF digestion in the rumen. Increasing level of corn decreased (linear, P < .07) in situ DM digestibility of SBH after 4, 8, and 12 h of incubation.

Ammonia↗

PubMed1992

PCR detection of the rat brain basic fibroblast growth factor (bFGF) mRNA containing a unique 3' untranslated region.

We utilized the reverse transcription-polymerase chain reaction (RT-PCR) to detect the presence of basic fibroblast growth factor (bFGF) messenger RNA in rat brain, ovary and kidney. The nucleotide sequence of the RT-PCR product revealed a novel 3' untranslated (UT) sequence in the rat basic FGF mRNA. In this sequence, as in the 3' UT regions of many growth regulatory genes, there is a high degree of conservation of A+T rich motifs which have been shown to play a major role in mRNA stability.

Animals↗

PubMed1992

Use of DNA probes to monitor nutritional effects on ruminal prokaryotes and Fibrobacter succinogenes S85.

We used DNA probes to study dietary effects on the prokaryotic population in the rumen. Procedures used to isolate and quantify prokaryotic 16S ribosomal RNA (rRNA) from the rumen using universal and species-specific DNA probes were evaluated. In this experiment, three ruminally fistulated steers were fed orchard-grass hay, and ruminal digesta were collected at 0, 3, and 9 h after offering hay (0800). Samples of ruminal digesta were taken from the interior portion of the digesta mat and from the fluid below the mat in the dorsal rumen. Freezing (-65 degrees C) and blending samples both increased (P less than .07) the yield of 16S rRNA from ruminal digesta. Extraction of prokaryotic rRNA was greater (P less than .04) when phenol buffered with sodium acetate was used than when it was buffered with hydroxymethyl-amino-methane. Prokaryotic 16S rRNA concentration of the fluid phase was similar (P greater than .10) at 0, 3, and 9 h after offering hay. Prokaryotic 16S rRNA concentration of the mat phase increased up to the 9 h after feeding. The proportion of Fibrobacter succinogenes remained constant in both digesta phases at all times measured. From these data we concluded that DNA probes can be used to monitor bacterial population shifts in the rumen.

Animals↗

PubMed1992

Performance, forage utilization, and ergovaline consumption by beef cows grazing endophyte fungus-infected tall fescue, endophyte fungus-free tall fescue, or orchardgrass pastures.

Two 120-d trials (May to September, 1988 and 1989) determined the effects of grazing tall fescue (two varieties) or orchardgrass on forage intake and performance by beef cows. Each summer, 48 cow-calf pairs grazed endophyte-infected Kentucky-31 tall fescue (KY-31), endophyte-free Mozark tall fescue (MOZARK), or Hallmark orchardgrass (OG) pastures (16 pairs/treatment). Forage OM intakes and digestibilities were determined during June and August each year. Cow and calf BW and milk production were determined every 28 d. During June of both years, OM intakes did not differ (P greater than .10) among treatments. During August of 1988, intakes were 18% lower (P less than .05) by KY-31 cows (1.6% of BW) than by MOZARK or OG cows (average 1.95% of BW); however, no differences (P greater than .10) were measured in August of 1989. Estimates of ergovaline consumption during June from KY-31 were between 4.2 (1988) and 6.0 mg/d (1989), whereas August estimates were between 1.1 (1988) and 2.8 mg/d (1989). Ergovaline in MOZARK estrusa was below detection limits, except in August of 1989. Cows that grazed KY-31 lost three times (P less than .01) more BW than cows that grazed MOZARK or OG (42 vs 9 and 13 kg, respectively). Milk production by KY-31 cows was 25% lower (P less than .01) than that by cows that grazed MOZARK or OG (6.0 vs average of 8.0 kg/d). Similarly, slower (P less than .01) calf gains were noted for KY-31 than for MOZARK or OG (.72 vs .89 and .88 kg/d, respectively). Cows grazing KY-31 experienced accelerated BW loss and reduced milk production and weaned lighter calves than did cows grazing MOZARK or OG. Decreased performance was not explained by consistently reduced forage intakes; hence, altered nutrient utilization was suspected.

Acremonium↗

PubMed1992

Site and extent of nutrient digestion by steers fed a low-quality bromegrass hay diet with incremental levels of soybean hull substitution.

Five ruminally and duodenally cannulated steers were fed bromegrass hay (H; 5.6% CP; 70.9% cell wall) substituted with 0, 15, 30, 45, or 60% soybean hulls (SH; 10.5% CP; 87.9% cell wall) at 90% of ad libitum DMI. Diets were made isonitrogenous (11% CP) by addition of isolated soybean protein (91.5% CP). Total ruminal VFA concentration, molar proportion of acetate, and molar acetate:propionate ratio increased (linear; P less than .02) with increasing level of SH substitution, but propionate (mol/100 mol) and ruminal fluid passage rate decreased (linear; P less than .01). Ruminal pH and ammonia concentration decreased more rapidly, and to a greater extent and duration, as level of SH increased; neither was decreased to levels considered detrimental to fiber digestion. Ruminal and total tract DM, OM, and cell wall digestibilities increased (linear; P less than .01), whereas total tract N digestibility decreased (linear; P = .03), as level of SH increased Total N flow to the duodenum increased (linear, P = .03) with increasing level of SH, and microbial N flow tended (cubic, P = .09) to increase. Microbial efficiencies were unchanged (P = .10) with SH level. True ruminal digestibilities of N did not differ (P greater than .10) among diets. Rate of in situ DM disappearance of H and SH was not influenced (P greater than .10) by SH substitution, although rate tended to be fastest with 30 and 45% SH (quadratic, P = .14). We infer from these data that SH can replace 60% of the DMI of a low-quality forage diet without decreasing OM or cell wall digestion.

Ammonia↗

PubMed1991

Digestibility of vegetative and mature tall fescue greenchop with or without alfalfa greenchop substitution.

Nine ruminally and duodenally cannulated steers (average BW 355 kg) were used to evaluate effects of prebloom alfalfa greenchop substitution at 20% of DMI on utilization of late-May (high quality; HQ; Period 1) and mid-August (low quality; LQ; Period 2) tall fescue greenchop. Alfalfa inclusion did not influence (P greater than .10) diet ad libitum DMI during Period 1 but it decreased (P less than .10) DMI during Period 2. Ruminal and total tract DM, cell wall, and GE digestibility of HQ were unaffected (P greater than .10) by alfalfa inclusion; however, digestibility of these constituents in LQ was increased (P less than .03) by alfalfa substitution. Alfalfa substitution did not influence (P greater than .10) dietary cell wall monosaccharide disappearance. Ruminal CP digestibility was greater (P less than .10) when steers received alfalfa, but microbial efficiency (grams of bacterial N/kilogram of OM truly digested in the rumen) was not enhanced (P greater than .10) by alfalfa inclusion in either HQ or LQ diets. There was a trend (P = .15) for greater microbial efficiency with alfalfa substitution to LQ. Ruminal particulate passage rate did not differ (P greater than .10) between treatments for either stage of maturity. Fluid passage rate was faster (P less than .10) in steers that received only LQ (7.1%/h) than in those fed LQ substituted with 20% alfalfa (5.0 %/h). Our data suggest that alfalfa inclusion in a low-quality fescue diet enhanced cell wall and GE digestibility.

Animal Feed↗

PubMed1991

Effects of grass maturity and legume substitution on large particle size reduction and small particle flow from the rumen of cattle.

Five ruminally and abomasally cannulated heifers (average weight 365 kg) were fed 6 kg/d of early (EOG) or late (LOG) maturity orchardgrass (OG) hay with or without replacement of EOG or LOG by 1.5 kg/d red clover hay (RC) in a 5 x 5 Latin square design. A fifth treatment, of LOG supplemented with 100 g/d casein (LOG + C), was used to evaluate the effect of supplemental protein. In situ fiber digestion, in vivo nutrient digestion and rate of passage from the rumen of large (retained on a 1.68-mm screen; labeled with La) and small (passed a 1.68-mm screen; labeled with Sm) EOG and LOG particles were determined in heifers fed these diets. Early maturity OG hay had 20% and 62%, respectively, greater (P less than .05) rates, and 61% and 73%, respectively, greater (P less than .05) extents of in situ NDF and ADF disappearance than LOG. Red clover substitution for OG increased (P less than .05) in situ extent of NDF disappearance by 6%. Early maturity OG large and small particles had 40% and 36%, respectively, greater (P less than .05) rates of passage than LOG. Large and small particle ruminal pool sizes were increased (P less than .05) by 115% and 33%, respectively, with LOG. Red clover substitution for OG increased (P less than .10) large and small particle output (kg/d) from the rumen by 15% and large particle rate of passage by 20%. Grass maturity may be affecting intake through rate of large particle size reduction and passage and small particle passage, although legume supplementation of OG may influence intake by increasing rate of large particle size reduction and passage.

Animal Feed↗

PubMed1991

Reduced blood flow to peripheral and core body tissues in sheep and cattle induced by endophyte-infected tall fescue.

Four wethers and 14 steers (environmentally heat stressed, 32 degrees C, 60% relative humidity) were evaluated for changes in blood flow induced by endophyte-infected tall fescue. Concentration of the ergopeptide ergovaline was used as an indicator of diet toxicity due to the endophytic fungus Acremonium coenophialum. Blood flow to specific tissues was measured using radiolabeled microspheres. Wethers received one of two dietary treatments for 30 d before determination of tissue blood flow: 1) a low-endophyte diet (less than .05 ppm ergovaline) or 2) a high-endophyte (1.18 ppm ergovaline) diet. Blood flows to the adrenal glands and skin covering the inner hind leg were less (P less than .10) in wethers consuming the high-endophyte diet than in those consuming the low-endophyte diet. Tissue blood flows in steers were determined on two occasions: 1) after steers had received a low- (less than .01 ppm ergovaline) or high-endophyte (.52 ppm ergovaline) fescue diet for 14 d and 2) 8 d after steers had been switched to a common, fescue-free diet. Blood flows to skin covering the ribs, cerebellum of the brain, duodenum, and colon were less (P less than .10) in steers consuming the high-endophyte diet. However, 8 d after consuming fescue-free diets, steers that had previously consumed the high-endophyte diet had greater (P = .08) blood flow to the coronary bands of the front hooves than steers that had consumed the low-endophyte diet. Blood flows to all other tissues were similar between treatments. We inferred from these experiments that the toxin(s) associated with endophyte-infected tall fescue caused decreased blood flow to peripheral and core body tissues and that this effect was abated within 8 d of removing the toxin(s).

Adrenal Glands↗

PubMed1990

Alpha 2-adrenoceptor blockade does not block feeding induced by neuropeptide Y in sheep.

We tested the hypothesis that blockade of central alpha 2-adrenergic receptors would prevent neuropeptide Y (NPY)-induced feeding. Nine young female sheep were fitted with lateral ventricula cannulas. Bolus intracerebroventricular (ICV) injection of 3 nmol of NPY increased feed intake after 30 min between 45 and 153% in three experiments. A bolus ICV injection of 400 or 100 nmol of the alpha 2-antagonist, yohimbine, either 5 or 30 min before NPY injection, did not attenuate this response. Instead, yohimbine increased feed intake over NPY-induced feeding by 52 to 55%. We interpret these data as evidence that the putative NPY feeding pathway in feed-sated sheep is not dependent on the type of alpha 2-adrenergic mechanism which can be blocked by ICV injection of yohimbine.

Animals↗

PubMed1990

Central nervous system injection of dynorphin-(1-13) overrides gastric satiety factors in sheep.

Signals from the gastrointestinal (GI) tract, arising during ingestion and digestion of food, are important in the termination of feeding. This study was carried out to determine whether the satiety triggered by specific GI stimuli in sheep could be reversed by central nervous system (CNS) administration of dynorphin, a putative endogenous kappa-opiate receptor ligand, which has been shown to be a potent feed-intake stimulant in many species. Rumen distension and increased intraruminal concentration of propionic acid (an energy substrate produced during fermentation in the rumen) both significantly decreased feed intake in fasted sheep. When either of these stimuli were combined with continuous 60-min lateral cerebroventricular injection of [D-Ala2]dynorphin A-(1-13) (0.32 nmol/min), feed intake returned to control levels. Increasing feed intake in food-producing animals is an important way of improving production efficiency. The findings of these experiments illustrate how manipulation of a CNS opioid system can modify the effects of feed intake-limiting factors generated by ingestion of a meal, thereby promoting greater feed intake.

Acetates↗

PubMed1990

Mefluidide treatment of tall fescue pastures: intake and animal performance.

Twelve Hereford heifers were used in a grazing experiment to determine intake and digestibility of tall fescue forage treated with the plant growth regulator mefluidide. Additionally, steer and heifer performance were evaluated after grazing tall fescue pastures or consuming hay harvested from pastures treated with mefluidide. Average forage OM intake by heifers was 47% greater (P less than .05) during July and 50% greater (P less than .05) during August for mefluidide-treated pastures than for untreated pastures. In vitro OM digestibility and indigestible ADF were compared for their ability to predict forage intake. The in vitro digestibility method produced more realistic intake data than the indigestible ADF method; however, trends in estimated forage intake were similar for both methods. Total tract particulate matter passage rates were similar (P greater than .10; 4.5 vs 4.1%/h), but mean retention times were shorter (P less than .05; 37.0 vs 46.9 h) when heifers grazed mefluidide-treated tall fescue. Steers grazing mefluidide-treated forage had greater (P less than .05) total weight gains than did steers grazing untreated tall fescue during a 168-d study (86 vs 69 kg). Heifers fed hay harvested from mefluidide-treated pastures also exhibited similar improvements in gain (49 vs 38 kg) because of increased (P less than .05) forage consumption (8.3 vs 7.3 kg/d) and greater (P less than .05) forage OM digestibility (65 vs 61%). Mefluidide treatment of tall fescue in early spring prolonged higher-quality herbage into midsummer and resulted in greater forage intake and animal performance.

Acetamides↗

PubMed1990

Mefluidide treatment of tall fescue pastures: forage quality.

Spring application of a plant growth regulator, mefluidide, to tall fescue (Festuca arundinacea Schreb.) pastures grazed from May to September reduced (P less than .05) available DM and digestible OM per hectare by 51 and 41%, respectively, compared to untreated pastures. However, seasonal averages for N, Ca and P content and in vitro OM disappearance (OMD) were greater (P less than .05) and NDF was lower (P less than .05) in tall fescue from mefluidide-treated pastures than in untreated pastures. Compared to hand-clipped samples, esophageal extrusa of tall fescue was 63% higher (P less than .05) in N (2.7 vs 1.7%) and 26% lower (P less than .05) in NDF (52.6 vs 69.9%) than hand-clipped tall fescue samples, regardless of treatment. Extrusa and hand-clipped herbage samples were similar (P greater than .10) in OMD during May and September, but OMD of extrusa was greater (P less than .05) during June, July and August compared to clipped samples. As a consequence of preventing stem elongation and seedhead formation earlier in the growing season, mefluidide treatment of tall fescue maintained forage quality at a higher level during midsummer.

Acetamides↗

PubMed1990

Blockade of satiety factors by central injection of neuropeptide Y in sheep.

The ability of neuropeptide Y (NPY) to stimulate feed intake was tested in combination with two treatments known to depress feed intake in sheep. Six ewe and three wether lambs (mean BW = 40 kg) fitted with lateral cerebral ventricular guide cannulas and ruminal cannulas had free access to a nutritionally complete, pelleted diet. Balloons placed into the rumen were filled with either 0, 30 or 60 ml of water/kg BW and left in place for 6 h; intake was measured. Based on the decline in feed intake observed with increasing balloon volume in the rumen, Exp. 2 was designed to test effects of NPY injection (0 or 3.0 nmol) into the lateral cerebral ventricle and ruminal distension (0 or 35 ml/kg BW) for 6 h. During the 6-h test period, feed intake was depressed (P less than .05) by intraruminal balloon distension, but feed intake was increased by NPY injection (P less than .05); no interaction between NPY and distension was detected. Ruminal evacuation revealed that digesta occupied only 43% of the rumen's total volume capacity. Balloons occupied 14% of capacity, whereas meal size in control sheep following a 1.5-h fast equaled 7% of capacity. In Exp. 3, intraruminal infusion of 8 mmol/min of propionate depressed (P = .11) feed intake, whereas NPY injection enhanced (P less than .05) intake. There was no interaction between NPY and propionate infusion. In none of these experiments was cumulative feed consumption at 24 h influenced. We conclude that NPY is a versatile feeding stimulant. It promotes feed intake in feed-satiated, ruminally distended and propionate-infused sheep.

Animals↗

PubMed1990

Effects of increasing dietary levels of endophyte-infected tall fescue seed on diet digestibility and ruminal kinetics in sheep.

Three experiments were conducted with sheep to determine the effects of 1) increasing the dietary concentration of ergovaline and 2) environmental temperature on site of nutrient digestion and ruminal passage rates. Dietary ergovaline concentration, a measure of endophyte-alkaloid concentration, was modified by substituting ergovaline-infected for noninfected tall fescue seed. Ruminal and total tract OM, NDF and cellulose digestibilities were less (P less than .10) and ruminal fluid dilution rate (%/h) and fluid outflow (liters/h) were greater (P less than .05) when diets contained 3 ppm ergovaline than when diets contained 0 ppm ergovaline. An interaction (P less than .05) between dietary ergovaline concentration (0 vs 1.5 ppm) and environmental temperature (27 vs 34 degrees C) was found for OM intake and NDF and cellulose digestion. Ruminal fluid dilution and outflow rates decreased (P less than .01) even though water consumption increased (P less than .01) with increasing temperature. Rectal temperature increased (P less than .01) when ergovaline and ergotamine tartrate were fed and when sheep were exposed to increased environmental temperature. Under the dietary (and environmental) conditions described, our results suggest that alkaloid(s) present in infected tall fescue seed inhibit ruminal fiber digestion and increase the sensitivity of sheep to heat stress.

Acremonium↗

PubMed1990

Effects of corn vs corn gluten feed on site, extent and ruminal rate of forage digestion and on rate and efficiency of gain.

Three digestion experiments and one growth experiment were conducted to determine site, extent and ruminal rate of forage digestion and rate and efficiency of gain by cattle offered alfalfa haylage supplemented with corn or dry corn gluten feed (CGF). In Exp. 1, eight steers were fed alfalfa haylage-based diets with substitution of corn for 0, 20, 40 or 60% of haylage in a 4 X 4 latin square. Increasing dietary corn substitution increased (P less than .05) OM, NDF and ADF digestion by steers but decreased (P less than .05) rate of in situ alfalfa DM digestion. In Exp. 2, five heifers were fed alfalfa haylage-based diets with increasing dietary levels of CGF in a 5 X 5 latin square. Increasing dietary CGF increased (P less than .05) OM, NDF and ADF digestion by heifers. In Exp. 3 and 4, cattle were fed alfalfa haylage-based diets containing either 20 or 60% corn or CGF. In Exp. 3, supplementation increased (P less than .05) OM and NDF digestion but level X supplement source interaction (P less than .05) occurred, with added CGF increasing OM and NDF digestion more than added corn. In Exp. 4, supplementation improved (P less than .05) DM intake, daily gain and feed efficiency. Dry matter intake and daily gain were greater (P less than .05) for 60% supplementation than for 20% supplementation. Overall, whereas increasing the level of dietary supplement increased (P less than .05) OM, NDF and ADF digestion, only corn addition decreased (P less than .05) rate of in situ alfalfa DM digestion. Daily gains and feed efficiencies were similar in cattle fed either corn or CGF with alfalfa haylage.

Animal Feed↗

PubMed1989

Postnatal development of vascularity in the inferior colliculus of the young rat.

The inferior colliculus in the rat midbrain is an auditory relay center whose functional maturation occurs postnatally. We examined by morphometry the vascularity and the nuclear profile density of the inferior colliculus in normal young rats at different ages (before and after the onset of auditory input). We also compared this region with a frontal region of the cerebral cortex in 24-day-old rats. The inferior colliculus from aldehyde-perfused Sprague-Dawley rats aged 5, 9, 14, and 24 days was analyzed by light microscopy of semithin plastic sections. The central region (mostly the central nucleus) was sampled at 5 levels representing its entire rostrocaudal extent. Patent-blood-vessel profiles were counted and classified according to their size and profile orientation. Counts of nuclear profiles in the same sections were also made. In the inferior colliculus of rats between 5 and 24 days of age, the small (less than 10-microns diameter) cross-sectioned vessel profiles increased over 6-fold in number per unit area. Correspondingly the vascular volume density, estimated by differential point counting, increased between these ages. However, there was a decrease in the number of neuronal and glial nuclear profiles per unit area, probably because of growth in the volume of the neuronal perikarya and processes, along with cell emigration reported to occur at early postnatal ages. This study has shown that an increase in vascularity in the central region of the rat inferior colliculus continues for up to 2 weeks after the onset of hearing.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗