Temperature induced peripheral blood flow changes in lizards

Summary The influence of local temperature changes within the posterior portion of the body on dorsal aorta blood flow ( ), femoral arterial pressure (P _a ), peripheral resistance (R), skin blood flow ( ) and skeletal muscle blood flow ( ) was examined in unanesthetized lizards (Iguana iguana andTubinambis nigropunctatus). In response to local heating of the hind legs and tail and increased,P _a was generally unchanged,R decreased and decreased or was unchanged (Fig. 2). It is suggested that the acquisition of heat may be favored by diverting the increase in away from the muscle to the warmer skin. In response to cooling and decreased,P _a was generally unchanged, R increased and increased or was unchanged. Hence, during cooling the retention of heat may be favored by diverting blood away from the skin to the deeper muscle. The muscle-skin shunt is under sympathetic control since following blockade with phenoxybenzamine HCL (Dibenzyline) muscle blood flow changes in response to temperature were qualitatively similar to those of skin (Fig. 4). These changes in peripheral circulatory patterns are independent of changes in heart rate or deep body temperature.Baker and Weathers were predoctoral and postdoctoral trainees, respectively, under USPHS Grant HE-05696. This study was also supported by NSF Grant GB-8523 and Los Angeles County Heart Association Grant 437IG.     

Estimation of surface charges in some biological membranes

Summary The resting membrane potential data existing in the literature for the giant axon of the squid, frog muscle and barnacle muscle have been analyzed from the standpoint of the theory of membrane potential due to Kobatake and co-workers. The average values derived for the effective charge density (where is a constant, , and represents the fraction of counterions that are free, and is the stoichiometric charge density in the membrane) present on the different biomembranes existing in their normal ionic environment are 0.3, 0.325 and 0.17 M for the squid axon, frog and barnacle muscles, respectively. On the assumption that the values of are 0.4 and 0.2 for nerve and muscle membranes, respectively, values of 0.75, 1.62 and 0.85 M have been derived for the stoichiometric charge density present in the respective biological membranes. These correspond to 1 negative charge per 222, 103 and 195 Å of the membrane area of the squid axon, frog and barnacle muscles, respectively.     

Altitudinal and seasonal effects on aerobic metabolism of deer mice

Summary I compared the maximal aerobic metabolic rates ( ), field metabolic rates (FMR), aerobic reserves ( -FMR), and basal metabolic rates (BMR) of wild and recently captured deer mice from low (440 m) and high (3800 m) altitudes. To separate the effects of the thermal environment from other altitudinal effects, I examined mice from different altitudes, but similar thermal environments (i.e., summer mice from high altitude and winter mice from low altitude). When the thermal environment was similar, , FMR, and aerobic reserve of low and high altitude mice did not differ, but BMR was significantly higher at high altitude. Thus, in the absence of thermal differences, altitude had only minor effects on the aerobic metabolism of wild or recently captured deer mice.At low altitude, there was significant seasonal variation in , FMR, and aerobic reserve, but not BMR. BMR was correlated with , but not with FMR. The significant positive correlation of BMR with indicates a cost of high , because higher BMR increases food requirements and energy use during periods of thermoneutral conditions.Abbreviations BMR basal metabolic rate - FMR field metabolic rate - partial pressure of oxygen - T _a ambient temperature - T _b body temperature - T _e operative temperature - maximal aerobic metabolic rate     

Likely linkage: Inv with Jk

Summary In a data base consisting of 1665 pairs of loci linkage between Inv and Jk is significant . Recombination is nearly the same in the two sexes . The reason why this linkage was not noticed earlier is discussed.     

Relationship between cardiac output and oxygen uptake at the onset of exercise

The purpose of the present study was to assess the relationship between the rapidity of increased gas exchange (i.e. oxygen uptake ) and increased cardiac output ( ) during the transient phase following the onset of exercise. Five healthy male subjects performed multiple rest-exercise or light exercise (25 W)-exercise transitions on an electrically braked ergometer at exercise intensities of 50, 75, or 100 W for 6 min, respectively. Each transition was performed at least eight times for each load in random order. The was obtained by a breath-by-breath method, and was measured by an impedance method during normal breathing, using an ensemble average. On transitions from rest to exercise, rapidly increased during phase I with time constants of 6.8–7.3 s. The also showed a similar rapid increment with time constants of 6.0–6.8 s with an apparent increase in stroke volume (SV). In this phase I, increased to about 29.7%–34.1% of the steady-state value and increased to about 58.3%–87.0%. Thereafter, some 20 s after the onset of exercise a mono-exponential increase to steady-state occurred both in and with time constants of 26.7–32.3 and 23.7–34.4 s, respectively. The insignificant difference between and time constants in phase I and the abrupt increase in both and SV at the onset of exercise from rest provided further evidence for a cardiodynamic contribution to following the onset of exercise from rest.     

Breathing pattern and growth: comparative aspects

Summary The resting oxygen consumption and breathing pattern of nine newborn and adult species (ranging in body size from mouse to human) have been compared on the basis of data collected from the literature. Minute ventilation is similarly linked to at both ages, the percent of extracted as O₂ about 2.2. Tidal volume/kg is an interspecies constant in newborns and adults, approximately 8 ml/kg. Breathing frequency decreases with the increase in size in a different way at the two ages: large species have newborns breathing at rates 2–3 times above the corresponding adults' values, while in the small species newborns and adults breathe at almost the same rate. Therefore the newborns of the smallest species have both and below the expected values, implying a greater inability to cope with the external demands than newborns of larger species. Several considerations indicate that in the smallest newborns the mechanical properties of the respiratory system could be a constraint to resting ventilations larger than observed. It is therefore possible that their low is the cause, and not the effect, of the relatively small .     

The nucleotide sequence ofBeneckea harveyi 5S rRNA

Summary The complete sequence of the 5S rRNA from the bioluminescent bacterium,Beneckea harveyi has been determined to be p U G C U U G G C G C C A U A G C G A U U-G G A C C C A C U G A (U) C U U C A U U C C-G A A C C A G A A G U G A A C G A A U U A-G G C C G A U G G U G U G U G G G G C U-C C C C A U G U A G A G U A G G A A U C G-C C A G G U (U)_OH.Two sites of sensitivity to ribonuclease T₂ cleavage were identified; at A₄₁ and either A₅₄ or A₅₅. Comparison with existing sequence information fromEscherichia coli andPhotobacterium phosphoreum clarifies the amount of diversity among the bioluminescent bacteria and provides further insight into their phylogenetic position. Sequence heterogeneities were encountered and the importance of these in interpreting 5S rRNA data is discussed.     

Respiratory responses of elite oarsmen, former oarsmen, and highly trained non-rowers during rowing, cycling and running

The position of the body and use of the respiratory muscles in the act of rowing may limit ventilation and thereby reduce maximal aerobic power relative to that achieved in cycling or running, in spite of the greater muscle mass involved in rowing. This hypothesis was investigated for three groups of male subjects: nine elite senior oarsmen, eight former senior oarsmen and eight highly trained athletes unskilled in rowing. The subjects performed graded exercise to maximal effort on a rowing ergometer, cycle ergometer and treadmill while respiratory minute volume and oxygen consumption were monitored continuously. The VE at a given during intense submaximal exercise (greater than 75% of maximal ) was not significantly lower in rowing compared with that in cycling and treadmill running for any group, which would suggest that submaximal rowing does not restrict ventilation. At maximal effort, and for rowing were less than those for the other types of exercise in all the groups, although the differences were not statistically significant in the elite oarsmen. These data are consistent with a ventilatory limitation to maximal performance in rowing that may have been partly overcome by training in the elite oarsmen. Alternatively, a lower maximal VE in rowing might have been an effect rather than a cause of a lower maximal if maximal was limited by the lower rate of muscle activation in rowing.     

Dynamics of cardiorespiratory function in Standardbred horses during different intensities of constant-load exercise

Summary Six Standardbred horses were used to evaluate the time course of pulmonary gas exchange, ventilation, heart rate (HR) and acid base balance during different intensities of constant-load treadmill exercise. Horses were exercised at approximately 50%, 75% and 100% maximum oxygen uptake ( max) for 5 min and measurements taken every 30 s throughout exercise. At all work rates, the minute ventilation, respiratory frequency and tidal volume reached steady state values by 60 s of exercise. At 100% max, the oxygen consumption ( ) increased to mean values of approximately 130 ml/kg·min, which represents a 40-fold increase above resting . At the low and moderate work rates, showed no significant change from 30 s to 300 s of exercise. At the high work rate, the mean at 30 s was 80% of the value at 300 s. The HR showed no significant change over time at the moderate work rate but differing responses at the low and high work rates. At the low work rate, the mean HR decreased from 188 beats/min at 30 s to 172 beats/min at 300 s exercise, whereas at the high work rate the mean HR increased from 204 beats/min at 30 s to 221 beats/min at 300 s exercise. No changes in acid base status occurred during exercise at the low work rate. At the moderate work rate, a mild metabolic acidosis occurred which was nonprogressive with time, whereas the high work rate resulted in a progressive metabolic acidosis with a base deficit of 16 mmol/l by 300 s exercise. It is concluded that the kinetics of gas exchange during exercise are more rapid in the horse than in man, despite the relatively greater change in in the horse when going from rest to high intensity exercise.Symbols and abbreviations E minute ventilation - V _T tidal volume - oxygen uptake - carbon dioxide output - oxygen pulse - ventilatory equivalent for oxygen - ventilatory equivalent for carbon dioxide - R respiratory exchange ratio - HR heart rate - SBC standard bicarbonate - STPD standard temperature and pressure dry - BTPS body temperature and pressure saturated - arterial oxygen content - arteriovenous oxygen content difference - Rf respiratory frequency     

Activity and oxygen consumption during hypoxic exposure in high altitude and lowland sceloporine lizards

Summary Resting rates of O₂ consumption against , exercise endurance times and during recovery from vigorous exercise were measured inSceloporus occidentalis captured near sea level and inS. graciosus captured above 2850 m. Oxygen consumption against was also measured inS. occidentalis captured above 2850 m. When was recorded continuously, as ambient was slowly reduced from 155 Torr, it became directly dependent upon ambient between 110 and 120 Torr. The critical for the high altitude lizards was lower than that for the lowland lizards, which enabled the former to maintain relatively higher 's when ambient was reduced below 120 Torr. The high altitude lizards also had significantly greater endurance when stimulated to exercise at 1600 m ( 130 Torr). Both the higher under hypoxia and the greater endurance roughly parallel a significantly greater maximum in the high altitude lizards. At a simulated altitude of 3600 m ( 100 Torr), maximum and rate of recovery of the O₂ debt calculated from post active were significantly reduced in the lowland but not the high altitude lizards. The effects of simulated altitude conditions on the lowland but not the mountaine animals indicate adaptations to altitude in these sceloporine lizards. We did not find any consistent relationship between organ/body weight ratios or hematocrit and our measures of endurance or the altitude at which the lizards were captured.     

Linkage analysis using multiple DNA polymorphic markers in normal families and in families with fragile X syndrome

Summary Linkage data, using the polymorphic markers 52A (DXS51), F9, 4D-8(DXS98), and St14(DXS52), are presented from 14 fragile X pedigrees and from 7 normal pedigrees derived from the collection of the Centre d'Étude du Polymorphisme Humaine. A multipoint linkage analysis indicates that the most probable order of these four loci in normal families is DXS51-F9-DXS98-DXS52. Recombination frequencies ( ) corresponding to maximum LOD scores ( ) were obtained by two-point linkage analysis for a nuber of linkage groups, including: DXS51-F9 ( =5.94, =0.03), F9-DXS98 ( =0.51, =0.26), F9-DXS52 ( =0.84, =0.27), and DXS98-DXS52 ( =0.32, =0.20). A multipoint linkage analysis of these loci, including the fragile X locus, was also performed for the fragile X population and the data support the relative order (DSX51, F9, DXS98)-FRAXA-DXS52. Recombination frequencies and maximum LOD scores, which again were derived from two-point linkage analyses, were obtained for the linkage groups DXS51-F9 ( =9.96, =0) and F9-DXS52 ( =0.07, =0.45), as well as for the groups DXS51-FRAXA ( =2.42, =0.15), F9-FRAXA ( =1.30, =0.18), DXS98-FRAXA ( =0.05 =0.36), and DXS52-FRAXA ( =2.42 =0.15). The linkage data was further tested for the presence of genetic heterogeneity both within and between the fragile X and normal families for the intervals DXS51-F9, F9-DXS52, F9-FRAXA, and DXS52-FRAXA using a modification of the A test. Except for the interval F9-FRAXA (P<0.10) there was no evidence of genetic heterogeneity for each of the various linkage groups examined. The heterogeneity detected for the interval F9-FRAXA, however, was most likely due to one family (Fx-28) that displayed very tight linkage between these two loci.     

Aerobic metabolism of the lizardVaranus exanthematicus: Effects of activity, temperature, and size

Summary Oxygen consumption was measured at rest and during spontaneous activity at body temperatures of 25 and 35°C in 14 fasting Savanna monitor lizards,Varanus exanthematicus ranging in weight from 172 to 7500 g. The allometric relationship between metabolic rate at 25°C and body weight (W) is given by: (ml O₂ STPD·g^–1·hr^–1)=0.88W ^–0.43 (Fig. 2). Although statistical comparisons are equivocal, this intraspecific size dependence exceeds that reported for interspecific comparisons among reptiles and other vertebrate groups (Fig 3). A reproducible diurnal pattern of activity was observed in undisturbed animals with minimum values of between 2400 and 0800 h (Fig. 1). Spontaneous activity and generally reached peak values between 1200 and 2000 hrs. The average ratio of active aerobic metabolic rate (AMR) to minimum (standard) aerobic metabolic rate (SMR) was 8.2. This voluntary AMR/SMR inVaranus exceeds the AMR/SMR for most reptiles stimulated to exhaustion. The high aerobic capacity is consistent with other evidence for efficient exchange and transport of respiratory gases inV. exanthematicus; e.g., low or absent intracardiac shunt flow resulting in high arterial saturation and low ventilation and perfusion requirements.     

Times to exhaustion at 100% of velocity at [(V)\dot]\textO\text2 \dot V{\text{O}}_{\text{2}} max and modelling of the time-limit / velocity relationship in elite long-distance runners

The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits _{max max} in 38 elite male long - distance runners _max = 71.4 ± 5.5 ml.kg^–1.min^–1 and _max = 21.8 ± 1.2 km.h^–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in _max. Tlim value was negatively correlated with _max (r = -0.362, p< 0.05) and _max (r = –0.347, p< 0.05) but positively with LT (%v _max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at _max in a homogeneous group of elite male long-distance runners was inversely related to _max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) .     

Physiological responses to cold (10° C) in men after six months' practice of yoga exercises

A study was conducted on 30 healthy soldiers (age: 40–46 years) to assess the effect of selected yogic exercises (asanas) on some physiological responses to cold exposure. They were randomly divided into two groups of 15 each. One group performed regular physical exercises of physical training (PT), while the other group practised yogic exercises. At the end of 6 months of training, both the groups were exposed together to cold stress at 10°C for 2 h, and the following parameters were periodically monitored during cold exposure: heart rate (fH), blood pressure (BP), cardiac output , oral temperature (T_or), skin temperature (T _sk), respiratory rate (fR), minute ventilation , oxygen consumption , and shivering response by integrated electromyogram (EMG). There were progressive increases inBP, fR, , , and and decreases infH,T _or andT _sk during cold exposure in both the groups. However, the decrease inT _or and the increases in and were relatively lower (P<0.01) in the yoga group as compared to the PT group. The shivering response appeared much earlier and was more intense in the PT group. These findings suggest that practice of yoga exercises may improve cold tolerance.     

Skeletal muscle [(V)\dot]O2 \dot V_{O_2 } in rat and lemming: Effect of blood flow rate

Summary The rate of oxygen consumption ( ) by skeletal muscle was investigated in isolated perfused hindlimbs of laboratory rats and lemmings (Lemmus). In both species, increased in proportion to blood flow rate, even at flow rates 4–5 times above resting level. The slope of the line relating to skeletal muscle blood flow was significantly greater in the lemming than in the rat. This may be related to the inverse relationship between body weight and metabolic rate. These data support the hypothesis that in small animals a dependent relationship exists between blood flow and skeletal muscle .     

Water economy in bird nests

Summary Nest humidity ( ) under an incubating bantam hen was measured at ambient ranging from 1.3 to 25.0 mmHg. Weight loss of eggs was recorded in clutches of varying size. Nest and ambient were also measured in wild incubating willow ptarmigan nests in dry and wet habitats.Nest increased linearly with ambient in a way predictable on the assumption that the water vapour conductance ( ) of brood patch skin, plumage and eggs were constant and independent of ambient . Nest was also dependent of clutch size. Egg dehydration was quantitatively predicted from measured values and the laws of diffusion.Our findings confirm earlier conclusions that the adult bird does not actively regulate nest at varying ambient . Birds can presumably achieve appropriate egg dehydration by a strategy combining nest site, nest construction, egg shell conductance and incubation behaviour which meets the requirements of their breeding climate.Abbreviations water vapur pressure - water vapur conductance - water flux     

Thermoregulation,gas exchange,and ventilation in Adelie penguins (Pygoscelis adeliae)

Summary Adelie penguins (Pygoscelis adeliae) experience a wide range of ambient temperatures (T _a) in their natural habitat. We examined body temperature (T _b), oxygen consumption ( ), carbon dioxide production ( ), evaporative water loss ( ), and ventilation atT _a from –20 to 30 °C. Body temperature did not change significantly between –20 and 20°C (meanT _b=39.3°C).T _b increased slightly to 40.1 °C atT _a=30°C. Both and were constant and minimal atT _a between –10 and 20°C, with only minor increases at –20 and 30°C. The minimal of adult penguins (mean mass 4.007 kg) was 0.0112 ml/[g·min], equivalent to a metabolic heat production (MHP) of 14.9 Watt. The respiratory exchange ratio was approximately 0.7 at allT _a. Values of were low at lowT _a, but increased to 0.21 g/min at 30°C, equivalent to 0.3% of body mass/h. Dry conductance increased 3.5-fold between –20 and 30°C. Evaporative heat loss (EHL) comprised about 5% of MHP at lowT _a, rising to 47% of MHP atT _a=30°C. The means of ventilation parameters (tidal volume [VT], respiration frequency [f], minute volume [I], and oxygen extraction [ ]) were fairly stable between –20 and 10°C (VT did not change significantly over the entireT _a range). However, there was considerable inter- and intra-individual variation in ventilation patterns. AtT _a=20–30°C,f increased 7-fold over the minimal value of 7.6 breaths/min, and I showed a similar change. fell from 28–35% at lowT _a to 6% atT _a=30°C.Abbreviations C thermal conductance - EHL evaporative heat loss - oxygen extraction - f respiratory frequency - MHP metabolic heat production - evaporative water loss - LCT lower critical temperature - RE respiratory exchange ratio - T _a ambient temperature - T _b body temperature - rate of oxygen consumption - rate of carbon dioxide production - I inspiratory minute volume - VT tidal volume     

Eingangs-ausgangsbeziehungen und modell eines drehreflexes der haustaubeColumbia livia

Pigeons sitting on a turntable are exposed to horizontal -ramp-and-hold stimuli (= -RP-stimuli; angular velocity) (Fig. 1). At the same time, the mean rateE(t) of impulses/0.1 s or 0.2 s ofM. abductor indicis, M. abductor pollicis orM. flexor pollicis is registered. If the rotation axis lies in or in front of the pigeon's head the muscles studied respond phasic-tonicly to an ipsilaterad -RP-stimulus; and purely tonicly or also phasic-tonicly to a contralaterad -RP-stimulus (Figs. 2C and 4). The heightE _P of the tonic response component is independent from the direction of rotation and is only determined by the height of the -plateau (Fig. 2A). The heightE _D of the phasic response component is dependent upon the rotation direction and is determined, at a given rotation direction, by (Fig. 2A) and by the ramp slope ( angular acceleration) (Fig. 3A). This and the dependence of the tonic component and, with some pigeons, also of the phasic component uponr (distance between pigeon and rotation axis) lead to the conclusion that the tonic component is caused by the centripetal accelerationb _p , and the phasic component is caused by the angular acceleration and, with some pigeons, by the tangential accelerationb _t. The influence of the acceleration components uponE _D andE _P is dependent upon the pigeon's position angle relativ to the radiusvectorr (Figs. 4 and 5). The tonic component is the response to a quasi-pitch or a quasi-roll of the pigeon during steady rotation. This results from a comparison of the -RP-responses of the pigeon in a radial or tangential position (Fig. 6A) to the pitch and roll responses (Fig. 6B). A model has been developed on the basis of the measured stimulus-response relations (Fig. 7). It contains three input channels (x -,u _t- andu _p-channel) with low-pass filters for the angular, tangential and centripetal acceleration. The channel gain depends upon . The sum(t) of all channel outputs is sent through a pure-time-delay element and finally through a half-wave rectifier with a threshold and an upper limitation. The transfer characteristics of the model agree rather well with those of the pigeon. The model can be interpreted in terms of neurophysiology.

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Teil einer Habilitationsschrift an der Mathematisch-Naturwissenschaftlichen Fakultät der Universität des Saarlandes.

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Herrn Prof. Dr. W. Nachtigall danke ich für die großzügige Unterstützung der Arbeit. Fräulein A. Jahner danke ich für die Assistenz und für die Anfertigung der Abbildungen, meiner Frau für die kritische Durchsicht des Textes. Frau Dr. M. Biederman-Thorson und Herrn Prof. Dr. D. Varjú bin ich für wertvolle Kritik dankbar. Die Arbeit wurde zum Teil aus Mitteln der Stiftung Volkswagenwerk finanziert, die Herm Prof. Dr. W. Nachtigall zur Verfügung standen.     

Are oxygen uptake kinetics at the onset of exercise speeded up by local metabolic status in active muscles?

To assess the rate-limiting factor of oxygen uptake ( ) kinetics at the onset of exercise, six healthy male sedentary subjects performed repeated one-legged constant-load cycle exercise. The one-legged constant-load exercise test consisted of two 5-min periods of pedalling at an exercise intensity of 50 W, with a 5-min rest between periods (these exercise periods, i.e. first and second exercises, were performed by the same leg). The exercise was then repeated using the other leg. In addition, two-legged incremental exercise was investigated to establish whether kinetics were affected by slower heart rate kinetics. The incremental exercise test consisted of two-legged pedalling first with the cycle unloaded as a warm-up for 5 min followed by 50-W exercise for 5 min. The exercise intensity was then increased to 100 W for 5 min. During exercise, gas exchange parameters were determined by the breath-by-breath method and cardiac output ( ) was determined continuously by an impedance technique with a computer-based automated system. To determine the kinetics of heart rate (HR), and , a best fit procedure was employed using least-squares criteria with a time delay, except during the initial increase. During the one-legged constant-load exercise test, kinetics were significantly accelerated by repeated exercise using the same leg. On the other hand, when the exercise was changed to the other leg, kinetics were significantly slower, although kinetics continued to be faster. During the incremental exercise test, although the HR response was slower at the transition from 50-W to 100-W exercise than at the transition from warm-up to 50-W exercise, there were no significant changes in kinetics. These findings suggest that kinetics may be affected by metabolic conditions in the muscle, but not by blood flow ( and/or HR) kinetics.     

Evidence for linkage of the gene causing familial Mediterranean fever to chromosome 17q in non-Ashkenazi Jewish families: second locus or type I error?

Familial Mediterranean fever (FMF) is an autosomal recessive disorder of unknown pathogenesis, characterized by recurrent, selflimited attacks of fever with synovitis, peritonitis, or pleurisy. Using DNAs from affected Israeli families, we have recently mapped the gene causing FMF (designated MEF) to the short arm of chromosome 16, with two-point lod scores in excess of 20. In this report we consider the possibility of a second FMF susceptibility locus. Before discovering linkage to markers on chromosome 16, we had found suggestive evidence for linkage to chromosome 17q, with the following maximal two-point lod scores: D17S74 (pCMM86), = 2.47, ( = 0.20); D17S40 (pLEW101), = 2.15( = 0.15); D17S35 (CRI-pP3-1), = 1.78 ( = 0.15); D17S46 (pLEW108), = 1.69 ( = 0.18), D17S254, = 2.30 ( = 0.20). Moreover, multipoint linkage analysis using D17S74 and D17S40 as fixed loci gave = 3.27 approximately 10 centimorgans (cM) telomeric to D17S40. Data with the chromosome 17 markers alone in our families suggested locus heterogeneity. Nevertheless, our families were not separable into complementary subsets showing linkage either to chromosome 16 or to chromosome 17. We also examined the possibility that the positive lod scores for chromosome 17 might reflect a secondary, modifying locus. By several measures of disease severity, families with positive lod scores for chromosome 17 loci had no worse disease than those with negative lod scores for these loci. We conclude that chromosome 17 does not encode a major FMF susceptibility gene for some of the families, nor does it encode a disease-modifying gene. Rather, it would appear that linkage to chromosome 17 is a false positive (type I) error. These results reemphasize the fact that a lod score of 3.0 corresponds to a posterior probability of linkage of 95%, with an attendant 1 in 20 chance of observing a false positive.