Biomedical subjects

C M Wood

Publications and source records attributed to C M Wood.

At least 19 recordsLinked to original sources

PubMed1992

Mechanisms of ion and acid-base regulation at the gills of freshwater fish.

This review examines the branchial mechanisms utilized by freshwater fish to regulate internal acid-base status and presents a model to explain the underlying basis of the compensatory processes. Rainbow trout, Oncorhynchus mykiss, and brown bullhead, Ictalurus nebulosus, were examined under a variety of experimental treatments which induced respiratory and metabolic acid-base disturbances. Acid-base regulation was achieved by appropriate adjustments of Na+ and Cl- net fluxes across the gills which, in turn, were accomplished by variable contributions of three different branchial mechanisms: 1) differential changes in Na+ and Cl- diffusive effluxes, 2) changes in internal substrate (H+, HCO3-) availability, and 3) morphological adjustments to the gill epithelium. Differential diffusive efflux of Na+ over Cl- was involved only during periods of metabolic alkalosis. The importance of internal substrate availability was demonstrated using a two-substrate model. According to the model, ionic flux rates (J(in)Cl-, J(in)Na+) are determined not only by the concentration of the external ion (Na+, Cl-) but also by the concentration of the internal counterion (H+, HCO3-). This system provides for an "automatic negative feedback" to aid in the compensation of metabolic acid-base disturbances. Morphological alteration of the gill epithelia and the associated regulation of chloride cell (CC) fractional area is an essential third mechanism which is especially important during respiratory acid-base disturbances. Specifically, fish vary the availability of the CC associated Cl-/HCO3- exchange mechanism by physical covering/uncovering of CCs by adjacent pavement cells.

Acid-Base Equilibrium↗

PubMed1992

Anterior subcapsular plaque cataract in hyperornithinaemia gyrate atrophy--a case report.

Hyperornithinaemia gyrate atrophy (HOGA) is a rare autosomal recessive disorder in which chorioretinal degeneration occurs with cataracts, myopia, and hyperornithinaemia. We report the case of an 18-year-old female who presented with the typical features of HOGA, including posterior subcapsular cataracts and elevated plasma ornithine. She later developed distorted vision in both eyes owing to wrinkling of the anterior lens capsules. Histological examination following lens extraction showed the wrinkling was caused by focal distortion from capsular fibrosis (anterior subcapsular plaque cataract). This specific lens change has not been linked previously with HOGA.

Adolescent↗

PubMed1992

Changes in pHi associated with activation of ion secretion in avian nasal salt gland cells.

The fluorescent pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)- carboxyfluorescein (BCECF) was used to determine changes in intracellular pH (pHi) associated with activation of secretion in isolated cells from the salt-secreting avian nasal gland. A correction procedure overcoming artifacts due to BCECF leakage is described. Resting pHi averaged 7.15 +/- 0.03 and was unaffected by the nominal removal of medium HCO3- or by the addition of the anion-exchange inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) but was significantly reduced by amiloride (7.07 +/- 0.02). Muscarinic activation of secretion resulted in a rapid intracellular acidification that was compensated by mechanisms which raised pHi to restore approximately resting levels within 5 min. The principal mechanism involved was amiloride-sensitive and independent of any sustained intracellular Ca2+ concentration change. Recovery of pHi was also aided by HCO3(-)-dependent and DIDS-sensitive mechanisms not seen in the resting cell. The direction of the latter was pHi-dependent, with DIDS further decreasing pHi in acidified cells and increasing pHi in alkalinized cells. This suggests that the DIDS-sensitive pathways are activated under conditions where pHi has been shifted away from resting levels in either direction and act primarily to restore resting pHi.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1992

Calcium transport by isolated skin of rainbow trout.

The skin overlying the cleithrum bone of freshwater-acclimated rainbow trout contains numerous mitochondria-rich (MR) cells, as detected by DASPEI fluorescence. This tissue was mounted in vitro in an Ussing-style chamber with fresh water on the mucosal surface and saline supplemented with bovine serum albumin on the serosal surface. The preparation developed a high transepithelial resistance and a small transepithelial potential (Vt), positive on the serosal side. Radioisotopic flux measurements indicated that the preparation actively transported Ca2+ from the mucosal to the serosal surface, as assessed by the Ussing flux ratio criterion. Ca2+ transport was positively correlated with MR cell density. Cortisol pretreatment in vivo reduced MR cell density and increased Vt but did not significantly alter Ca2+ fluxes. Ca2+ transport was unaffected by adrenergic agonists (10(-5) mol l-1 adrenaline, clonidine, isoprenaline) or cyclic AMP stimulants (10(-3) mol l-1 dibutyryl cyclic adenosine monophosphate, db-cAMP, plus 10(-4) mol l-1 isobutylmethylxanthine, IBMX) applied to the serosal surface. The Ca2+ ionophore ionomycin (1 x 10(-6)-3.2 x 10(-6) mol l-1 on the mucosal surface) increased both unidirectional Ca2+ fluxes and caused Ca2+ to accumulate within the epithelium. Lanthanum (10(-4) mol l-1) did not inhibit unidirectional Ca2+ fluxes, but apparently displaced Ca2+ from binding sites on the mucosal surface. Unlike Ca2+, movements of Na+ and Cl- across the epithelium were passive, as assessed by the flux ratio criterion, and neither adrenaline nor db-cAMP plus IBMX had any effect on Na+ or Cl- fluxes or electrical properties. These results indicate that ion transport across the skin mediated by MR cells ('chloride cells') contributes to Ca2+ but not to NaCl balance in freshwater trout.

Acclimatization↗

PubMed1992

Gas exchange, metabolite status and excess post-exercise oxygen consumption after repetitive bouts of exhaustive exercise in juvenile rainbow trout.

Juvenile rainbow trout (approximately 6 g) were exercised to exhaustion in two 5 min bouts given 6 h apart. Resting levels of whole-body lactate and glycogen were restored prior to the second bout. The rate of O2 consumption increased about threefold 5 min after each bout of exercise, while recovery time decreased from 4 h after the first bout to 2-3 h after the second. The excess post-exercise oxygen consumption, i.e. 'oxygen debt', was significantly reduced by 40% after the second exercise bout, despite almost identical rates of lactate clearance and glycogen resynthesis. The rates of CO2 and ammonia excretion increased sixfold and threefold, and recovery times decreased from 4-6 h to 3 h and from 3 h to 1.5 h, respectively. After the first bout, whole-body lactate levels peaked at 5 min post-exercise at about 8.5 times pre-exercise levels. After the second bout, lactate levels peaked at 0 min post-exercise and fell more rapidly during recovery. Whole-body glycogen levels decreased by 70% and 80% and ATP levels decreased by 75% and 65% after the first and second bouts, respectively, while glucose levels increased about 1.5-fold immediately after both bouts. Creatine phosphate levels decreased by 70% and 80% after the first and second bouts, respectively. After 6 h of recovery, creatine phosphate levels were higher after the second bout than after the first. These findings suggest that exhaustive exercise may cause a 'non-specific' increase in metabolic rate not directly related to the processing of metabolites, which is reduced upon a subsequent exercise bout. This is in contrast with the classical 'oxygen debt hypothesis', which states that the oxygen debt and lactate clearance are linked. Furthermore, it appears that two sequential exercise bouts are sufficient to induce a 'training effect', i.e. improved rates of metabolic recovery.

Adenosine Triphosphate↗

PubMed1992

Effect of feeding organic acids on selected intestinal content measurements at varying times postweaning in pigs.

Pigs weaned at 21 d of age (n = 72) were fed a 20% CP corn-soybean meal-based diet (control) with 1.5% fumaric or 1.5% citric acid added to observe the effect of these acids on the pH, chloride ion concentration (Cl-), VFA profile, and microflora population in the stomach, jejunum, cecum, and lower colon contents at -2, 0, 3, 7, 14, and 21 d postweaning. Feeding organic acids had no appreciable effect (P greater than .10) on stomach jejunum, cecum, or lower colon pH, Cl-, VFA profile, or microflora populations, except for increasing the concentration of fumaric acid in the stomachs of pigs fed fumaric acid. The pH of the gastrointestinal tract generally decreased from -2 to 21 d postweaning with no corresponding change in Cl- over time. No age effects on total anaerobic culture counts were observed except in the stomach, where counts decreased from -2 to 3 d postweaning. Clostridia counts generally decreased after weaning in all intestinal sections. Lactobacillus counts were usually lower at d 0 and 3 and greatest at d 7 postweaning in the stomach, jejunum, and lower colon, but no age effect was observed for concentration of cecum lactobacilli. Escherichia coli counts generally increased after weaning to 3 and 7 d postweaning. Intestinal content measurements were affected by postweaning age but were not affected by feeding organic acids.

Age Factors↗

PubMed1992

Effect of evening or morning weaning and immediate or delayed feeding on postweaning performance of pigs.

Weanling pigs (n = 176), 21 to 26 d of age (average initial weight, 7.1 kg), were used to evaluate the effects of weaning time (evening vs morning) and feeding time (immediate vs delayed) on postweaning performance. Pigs were randomly allotted within litters to four treatments in a 2 x 2 factorial arrangement as follows: 1) weaning at 2000 with immediate feeding, 2) weaning at 2000 with 12-h delayed feeding, 3) weaning at 0800 with immediate feeding, and 4) weaning at 0800 with 12-h delayed feeding. A 12:12 light:dark photoperiod was maintained. Four pigs were held per pen, and all pigs were given ad libitum access to a 20% CP corn-soybean meal diet with 15% dried whey throughout the 28-d study. The interactions between weaning and feeding times were not significant. During the 28-d period, pigs weaned at 2000 consumed 5% more feed (P less than .10) and grew 6% faster (P less than .05) than pigs weaned at 0800. Feed to gain ratios were similar for both time treatments. Variance of ADG within pens as measured by range, logarithm of variance, and CV were generally smaller for pigs weaned at 2000 than for pigs weaned at 0800 with no effect of feeding time. Pigs fed immediately after weaning and those delayed for 12 h had similar overall feed consumption, ADG, and feed to gain ratios. Weaning pigs in the evening enhanced performance, perhaps by better matching the normal diurnal eating and activity patterns and weaning time.

Animal Feed↗

PubMed1992

Efficacy of altrenogest in synchronizing estrus in two swine breeding programs and effects on subsequent reproductive performance of sows.

In two herds that used different breeding and housing schemes, altrenogest (15 mg/d) was fed for 14 d to gilts or 10 d to sows in .45 kg of a diet formulated to meet or exceed their nutrient requirements. In Herd 1 (five breeding seasons per year), 63 of 123 gilts and 40 of 70 sows in seven replications were fed in individual crates to ensure proper intake. In Herd 2 (continuous breeding), 244 of 484 gilts in 20 replications received the treated feed in individual feeding stalls to which animals had free access. Average and median days to estrus were reduced (P less than .01) for treated gilts and sows compared with controls in both herds. Of 29 treated gilts that did not mate or become pregnant, three had cystic follicles, compared to 1 of 14 controls. There were no statistically significant treatment differences in litter size born or number of stillborn pigs in either herd, but farrowing rates of cycling gilts were 8% lower (P less than .05) in Herd 2 for treated gilts than for controls. Overall, altrenogest could be a valuable tool for improving reproductive efficiency by allowing producers to better control the estrous cycle.

Administration, Oral↗

PubMed1991

Gastrointestinal motor effects of erythromycin in humans.

The effects of an antibacterially effective IV dose of erythromycin on gastrointestinal motor activity were investigated in eight normal healthy human volunteers in the fasted state and the fed state. Motor activity was recorded by a multilumen manometric tube. Data were analyzed visually and by a computer method. Blood samples were obtained for erythromycin and motilin assays. In the gastric antrum, erythromycin significantly increased the total duration, amplitude, and area under contractions from 0 to 60 minutes and frequency of contractions from 0 to 30 minutes from the start of its infusion in the fasted state. A similar response in the fed state occurred mostly from 0 to 30 minutes after the start of erythromycin infusion. By contrast, erythromycin inhibited the frequency and decreased the duration of small intestinal contractions in the fed state but had no effect in the fasted state. The gastric motor response was related to the plasma concentration of erythromycin, but not to plasma motilin. Erythromycin significantly shortened the duration of migrating motor complex disruption by a meal. Erythromycin also induced symptoms of upper abdominal pain, bloating, and nausea. Abdominal pain was related to strong antral contractions in both fasted and fed states; bloating occurred only in the fed state. Nausea occurred in both fasted and fed states, but it was not related to any specific pattern of motor activity. It is concluded that the strong antral contractions induced by erythromycin may accelerate the rate of gastric emptying, but they may also be responsible for causing the sensations of upper abdominal pain and bloating. The motor response to erythromycin is less during the fed than during the fasted state. The strong antral contractions induced by erythromycin are not mediated by the release of motilin.

Abdominal Pain↗

PubMed1991

Intracellular acid-base responses to environmental hyperoxia and normoxic recovery in rainbow trout.

Exposure of rainbow trout to environmental hyperoxia (PIO2 approximately 530 Torr) resulted in an extracellular respiratory acidosis which was fully compensated by 72 h; return to normoxia (PIO2 approximately 145 Torr) at this time induced a metabolic alkalosis which was corrected by 24 h. Intracellular pHi ([14C]DMO method), fluid volumes [3H]PEG-4000 method), and electrolytes were monitored. Environmental hypercapnia (PICO2 approximately 6.5 Torr) was employed to confirm that intracellular responses were specific to respiratory acidosis. Gill pHi did not change during respiratory acidosis despite a very low non-HCO3- buffer capacity, but gill ICFV decreased markedly. A large loss of gill intracellular [Cl-]i in excess of [Na+]i, combined with a substantial gain in [K+]i, contributed to gill pHi regulation by raising branchial [SID]i. In weakly buffered brain tissue, active adjustment of pHi started within 3 h, but two well buffered tissues, RBC and white muscle, exhibited compounding metabolic acidoses during the first 12-24 h. The muscle response was associated with small increases in ICFV and [Cl-]i, and a large decrease in [K+]i which reduced muscle [SID]i. We hypothesize that this initial export of K+ and basic equivalents served to regulate pH in more critical compartments (e.g. gills, brain) at the expense of muscle acidosis. By 48 h, pHi restoration in all tissues was complete, in advance of pHe regulation (72 h). Return to normoxia at 72 h elevated muscle, brain, and gill pHi, but there was no evidence of a comparable 'altruistic' role of muscle during this metabolic alkalosis. Regulation of pHi was complete by 24 h recovery, accompanied by partial or complete restoration of intracellular ions and fluid volumes.

Acid-Base Equilibrium↗

PubMed1991

The oxygen debt hypothesis in juvenile rainbow trout after exhaustive exercise.

A 5 min bout of exhaustive exercise in 2-3 g rainbow trout resulted in a 2.0-2.5 fold increase in oxygen consumption (MO2), a 5-fold increase in whole-body lactate (LAC) levels and a near depletion in whole-body glycogen (GLY), ATP and creatine phosphate (CP) stores; glucose, ADP and AMP did not change. Recovery of MO2 and LAC was complete by 6 h, by which time GLY had stabilized at about 65% resting levels without further recovery through 24 h. Complete recovery of ATP required 1.0-1.5 h, whereas restoration of CP required only 5 min. The MO2 recovery curve was resolved into an initial fast component (t1/2 = 0.23 h) and a second slower component (t1/2 = 2.1 h), comprising approximately 20% and 80% respectively of the excess post-exercise oxygen consumption (EPOC). The fast component was satisfactorily accounted for by the standard components of the 'alactacid O2 debt'. However, the slow component could not be completely explained by changes in whole body LAC and GLY during recovery based on scenarios of either oxidation or GLY resynthesis as the primary fate of LAC. The classical 'O2 dept hypothesis' (Hill and Lupton, Quart, J. Med. 16: 135-171, 1923; Margaria et al., Am. J. Physiol. 106: 689-715, 1933) cannot be the complete explanation of EPOC in the trout.

Adenosine Triphosphate↗

PubMed1991

Assignment of the human prohibitin gene (PHB) to chromosome 17 and identification of a DNA polymorphism.

Prohibition is a recently identified antiproliferative protein whose exact role in the cell is under investigation. To determine the human chromosomal location of the prohibition gene (PHB) and whether this site corresponds to that of any suspected tumor suppressor gene, we have analyzed DNA from three sources by hybridization analysis: mouse--human hybrid cell lines, hybrid cell lines containing portions of human chromosomes, and human metaphase chromosomes in situ. All three techniques confirm a location in the region 17q21-q22, a region genetically linked to early-onset human breast cancer. Further analysis will be required to establish the significance of this relationship; Southern hybridizations show a polymorphic EcoRI site that may be useful for this purpose.

Blotting, Southern↗

PubMed1991

Prohibitin, an evolutionarily conserved intracellular protein that blocks DNA synthesis in normal fibroblasts and HeLa cells.

Genes that act inside the cell to negatively regulate proliferation are of great interest because of their implications for such processes as development and cancer, but these genes have been difficult to clone. This report details the cloning and analysis of cDNA for prohibitin, a novel mammalian antiproliferative protein. Microinjection of synthetic prohibitin mRNA blocks entry into S phase in both normal fibroblasts and HeLa cells. Microinjection of an antisense oligonucleotide stimulates entry into S phase. By sequence comparison, the prohibitin gene appears to be the mammalian analog of Cc, a Drosophila gene that is vital for normal development.

Amino Acid Sequence↗

PubMed1991

A new in vitro assay for carbon dioxide excretion by trout red blood cells: effects of catecholamines.

A new in vitro assay was developed and critically characterized to measure the rate of CO2 excretion by trout red blood cells (RBCs) from HCO3- in their natural plasma under normal in vivo conditions of acid-base status. The assay is based on the addition of [14C]bicarbonate to the whole blood and collection of the resultant 14CO2 in the overlying gas phase. The assay simulates the exposure of blood passing through the gills, and measured CO2 excretion rates are representative of those occurring in vivo. Rates are linear over the 3 min time course of the assay, related to haematocrit in a non-linear fashion, elevated by the addition of carbonic anhydrase, reduced by blockade with acetazolamide, and sensitive to variations of equilibration PCO2. Large variations in plasma [HCO3-] have only a small effect on CO2 excretion rates when the blood is chronically equilibrated at these levels. Acute elevations in [HCO3-], however, create a non-equilibrium situation, resulting in large increases in CO2 excretion. When the blood is acidified, to duplicate typical post-exercise metabolic acidosis, adrenaline causes a marked inhibition of RBC CO2 excretion. The response is transient, reaching a peak 5-8 min after addition of adrenaline and disappearing by 30-60 min. The magnitude of the adrenergic inhibition is correlated with the magnitude of the RBC pHi regulatory response, expressed as the RBC transmembrane pH difference (pHe-pHi). These results support the 'CO2 retention theory' explaining observed increases in blood PCO2 in vivo after exhaustive exercise and catecholamine infusions in fish.

Animals↗

PubMed1991

Adrenergic inhibition of carbon dioxide excretion by trout red blood cells in vitro is mediated by activation of Na+/H+ exchange.

We have used a sensitive new technique to assess the mechanism(s) of adrenergic inhibition of rainbow trout (Oncorhynchus mykiss) red blood cell (RBC) carbon dioxide excretion in vitro. The effect was only apparent using blood acidified to simulate metabolic acidosis. Red blood cell CO2 excretion was inhibited in a dose-dependent manner by physiologically relevant concentrations of noradrenaline (10-1000 nmol l-1) or adrenaline (100-1000 nmol l-1). The beta-adrenoceptor antagonist propranolol abolished the inhibitory effect of adrenaline, whereas the alpha-adrenoceptor antagonist phentolamine was without effect. The action of noradrenaline on RBC CO2 excretion was mimicked by the beta-adrenoceptor agonist isoproterenol, but not by the alpha-adrenoceptor agonist phenylephrine. Therefore, adrenergic inhibition of CO2 excretion is mediated by RBC beta-adrenoceptors, presumably of the beta 1 subtype. The Na+/H+ exchange inhibitor amiloride effectively blocked adrenergic stimulation of Na+/H+ exchange (as indicated from measurements of pHe and RBC pHi) and entirely prevented the inhibition of CO2 excretion. Noradrenaline significantly reduced the rate of CO2 excretion even in the presence of the Cl-/HCO3- exchange inhibitor SITS. Therefore, adrenergic inhibition of CO2 excretion is accomplished via activation of RBC Na+/H+ exchange rather than by a direct inhibition of Cl-/HCO3- exchange. The observed relationship between CO2 excretion rates and the RBC transmembrane pH difference (pHe-pHi) and the occurrence of the inhibition only at low pHe provide further evidence of the linkage with RBC Na+/H+ exchange. We suggest that adrenergic activation of RBC Na+/H+ exchange impedes CO2 excretion by causing a rise in intracellular HCO3- levels concurrent with a reduction of intracellular PCO2. The net result is a reduced gradient for HCO3- entry into the RBC in conjunction with a diminution of the outwardly directed PCO2 gradient. Thus, the rate of formation of CO2 from the dehydration of plasma HCO3- is reduced and, in turn, a portion of this CO2 is not excreted but recycled through the red blood cell.

Adrenergic Antagonists↗

PubMed1991

Evaluation of methods of providing supplemental heat to newborn pigs during and after farrowing.

Two experiments were conducted to evaluate systems of providing supplemental heat to newborn pigs during and after farrowing. In Exp. 1, 35 sows were randomly allotted to farrowing crates with two supplemental heat treatments: 1) two lateral 250-watt heat lamps; and 2) two lateral heat lamps, plus a 250-watt heat lamp behind the sow during farrowing. In Exp. 2, 72 sows were randomly assigned to farrowing crates with four supplemental heat treatments: 1) one lateral 250-watt heater; 2) one lateral heater plus a 250-watt heater behind the sow during farrowing; 3) a hover with 100-watt light bulb; and 4) a hover with light bulb plus heater behind the sow during farrowing. The average farrowing house temperature was 18.9 degrees C in Exp. 1 and 21.6 degrees C in Exp. 2. Results showed no significant treatment effects on preweaning pig survival or growth rates in either experiment. Thus, providing a heat lamp at the rear of the sow during parturition was not beneficial and would increase operating costs. Hovers have a higher initial cost than conventional heat lamps or heaters, but they would have a much lower operating cost. Hovers may offer swine producers a way of reducing energy costs without affecting preweaning pig survival and performance.

Animal Husbandry↗

PubMed1991

Effects of dietary pH and phosphorus source on performance, gastrointestinal tract digesta, and bone measurements of weanling pigs.

Crossbred pigs (n = 144, average age and weight = 28 +/- 3 d, 7.5 kg) were used in two 6-wk trials to assess the effects of dietary pH and P source on growth performance, gastrointestinal digesta pH and chloride ion concentration (Cl-), and bone characteristics. Treatments were randomly allotted within blocks (based on weight within gender) to a 3 x 2 factorial arrangement with three dietary pH levels (5.4, 6.0, and 6.7) and two P sources: dicalcium phosphate (DCP) and defluorinated phosphate (DFP). Pigs fed the pH 6.7 diet had reduced ADG (P less than .01) and average daily feed intakes (ADFI; P less than .001) during wk 1 to 3 and overall compared with pigs fed the pH 6.0 diet, but ADG and ADFI were not affected when the pH 5.4 diet was fed. There was a dietary pH x P source interaction (P less than .05) for ADFI. Pigs had decreased ADFI as dietary pH was increased from 6.0 to 6.7 for both DCP and DFP, but ADFI was similar for the pH 6.0 and 5.4 diets with DFP, whereas ADFI was greater for the pH 5.4 diet with DCP. Dietary pH did not influence ADFI:ADG ratio (F:G; P greater than .05), and P source had no effect (P greater than .05) on either ADG, ADFI, or F:G.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1991

Use of an animal model in situations of limited subclass numbers and high degrees of relationships.

Breeding value estimation procedures for two traits with moderate and high heritability were evaluated by using a single-trait animal model and computer-simulated data designs. Of interest were the effects of differing numbers of animals and degrees of relationships among animals within and across contemporary groups (tests). Test effects were assumed fixed and animal effects were assumed random. Family size, number of families per contemporary group, and degree of genetic relationships within and across contemporary groups were varied to determine interrelationships among the factors. Results were compared on the basis of accuracy by using both the correlation of true and estimated breeding values and the prediction error variance obtained from the inverse of the coefficient matrix of the mixed-model equations. Small contemporary groups in conjunction with evaluation of closely related families caused average accuracy to decrease relative to that obtained with the same number of unrelated animals because genetically related animals were less accurately evaluated relative to one another. Connecting contemporary groups with a genetic relationship matrix formed a large set of interdependent equations and improved the average accuracy of predicted breeding values. The slight decrease in accuracy for genetically related animals was more than offset by the increase in accuracy of evaluation for their unrelated test mates because the proportion of fixed effects to random effects was smaller. Care must be exercised in designing evaluation schemes involving small populations, and the decision of which fixed effects to include in the model is critical.

Animals↗