[The precursors and effectors of human lymphokine-activated killer (LAK) cells]

Natural killer cells were enriched in the second fraction (F2) of discontinuous Percoll density gradients from human PBL after centrifugation, whereas T lymphocytes were enriched in F4. The cytotoxicity against K562 by F2 LAK (F2 cells activated by rIL2) was higher than that of F2 cells. F2 LAK also acquired the ability to lyse NK-resistant tumor cell lines and noncultured lung cancer cells (6 out of 9 cases). All these activities of F2 LAK cells were significantly higher than those of F4 LAK cells. Besides, F2 LAK exhibited higher level of lysis against noncultured lung cancer cells than did LAK derived from PBL. Enzyme-labeled immunocytochemistry staining showed that the number of CD16+ and CD8+ cells in F2 was much more than that in F4. So the higher lytic ability of F2 LAK might come from two kinds of precursors: CD16+ typical NK cells and MHC unrestricted CD8+, NK-like' cytotoxic T lymphocytes. The number of CD4+ cells in F4 was much more than that in F2. They shouldn't be the precursors of LAK cells, otherwise the lytic ability of F4 LAK should be higher than that of F2 LAK. After being cultured with rIL2 for 3 days, F2 cells exhibited proliferative response. But the percentage of CD16+ and CD8+ cells in F2 LAK did not change much, and remained much higher than that in F4 LAK. So the effector cells of short-term cultured LAK might be the activated CD16+ NK cells and CD8+, NK-like' cytotoxic T lymphocytes as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Antitumor agents. 126. Novel 4 beta-substituted anilino derivatives of 3',4'-O,O-didemethylpodophyllotoxin as potent inhibitors of human DNA topoisomerase II

A series of derivatives of 3',4'-O,O-didemethylpodophyllotoxin have been synthesized and evaluated for their inhibitor activity against neoplastic cell growth (KB) and against human DNA topoisomerase II as well as for their activity in causing cellular protein-linked DNA breakage. The results show that the compounds possessing a 4 beta-anilino moiety either unsubstituted or substituted at the para (F, COOCH3, COCH3, CN, CH2CN, NO2) or meta (OH) positions or with an ethylenedioxy moiety showed the same or greater activity than etoposide in causing cellular protein-linked DNA breakage and in inhibiting DNA topoisomerase II. However, compared to the corresponding 4'-O-demethyl analogues, the 3',4'-O,O-didemethyl compounds have a similar potency in inhibition of DNA topoisomerase II but are less active in causing cellular protein-linked DNA breakage. Complete correlation between the three biological activities--cytotoxicity, inhibition of DNA topoisomerase II, and induction of protein-linked DNA breakage--was also not observed. This supports the possibility that the biological determinants of action among these compounds may be different.

Evaluation of closure integrity after multiple penetrations

The purpose of this investigation was to simulate in-use testing of closures to determine how many doses could be reasonably withdrawn from a multiple dose vial of a product without compromising the integrity of the closure. Four types of studies were done: 1) a simulated in-use test, 2) a coring test development study, 3) effect of sterilization on coring, and 4) exploratory studies of closure leakage after multiple penetrations. A modified drill press was used for the studies. West 1888 and West 1535 closures were evaluated by the simulated in-use test using a 26G Needle. The results indicated that few particles were generated after 20 penetrations of both closures. There was a marked increase in particles after 30 penetrations. When sterilized closures were tested, it was found that West 1888 generated no particles after 10 insertions with 21G and 18G needles, but there was an increase in the number of particles after 20 insertions. With West 1535, particles were generated after only 10 insertions. Interestingly, autoclaved closures released fewer particles than closures that were not autoclaved. Leakage was observed only from West 850 closures and only under relatively high pressure differential conditions.

The activation of bone marrow macrophages 24 hours after thermal injury

We determined the effect of thermal injury on the in vitro production of the immunoactive substances tumor necrosis factor, interleukin 1, prostaglandin E2, and complement component C3 by lipopolysaccharide-stimulated guinea pig bone marrow macrophages and on the cytotoxicity of these cells. Macrophages from burned animals produced different amounts of these mediators compared with unburned animals at certain culture times, suggesting that thermal injury could program the bone marrow cells to respond differently from normal cells to in vitro stimulation with lipopolysaccharide. Also, the macrophages from burned animals displayed greater cytotoxicity towards L929 target cells. These results suggest that there is a complex interaction among cellular secretory products, especially after thermal injury, that may be important in host defense.

Genetic Consequences of Blocking Polar Body I with Cytochalasin B in Fertilized Eggs of the Pacific Oyster, Crassostrea gigas: I. Ploidy of Resultant Embryos

The effect of blocking polar body I (PB1) with cytochalasin B (CB) on the ploidy of embryos was studied in the Pacific oyster, Crassostrea gigas. To block the release of PB1, fertilized eggs were treated with CB (1.0 μg/ml) for 15 min beginning at 5 min post-fertilization at 25°C. The CB treatment and its control were repeated in three crosses. Ploidy of 8-h-old embryos was determined with karyological analysis. In control groups, the majority of the cells (89.3%) had a diploid number of 20 chromosomes, although spontaneous haploids (0.7%), triploids (1.3%) and aneuploids (8.7%) were also encountered. In CB-treated groups, only 4.5% of the cells remained as diploid, and the majority were either triploid (15.6%), tetraploid (19.4%) or aneuploid (57.6%). Despite variation among the three crosses, contingency Chi-square analysis showed that the occurrence of triploids, tetraploids and aneuploids had a significant (P = 0.0001) dependence on the CB treatment. The majority of the aneuploids fell into two groups containing either 23-25 or 35-37 chromosomes. The production of triploids, tetraploids and aneuploids in specific distributions suggests that blocking PB1 complicates subsequent chromosome segregation.

Genetic Consequences of Blocking Polar Body I with Cytochalasin B in Fertilized Eggs of the Pacific Oyster, Crassostrea gigas: II. Segregation of Chromosomes

The effect of blocking polar body I (PB1) with cytochalasin B (CB) on subsequent chromosome segregation was studied in fertilized eggs of the Pacific oyster, Crassostrea gigas. To block the release of PB1, fertilized eggs were treated with CB (1.0 μg/ml) for 15 min beginning at 5 min post-fertilization at 25{deg}C. Chromosome segregation in both control and CB-treated eggs was analyzed with an acetic orcein stain. In untreated eggs, ten maternal tetrad chromosomes went through meiosis I and II, and released two polar bodies, reaching a haploid number of 10 chromatids. In CB-treated eggs, meiosis I proceeded normally and produced two groups of dyads, ten in each group. However, blocking PB1 dramatically changed chromosome segregation in meiosis II. In the majority of the treated eggs (68%), the two groups of dyads from meiosis I entered meiosis II through a "tripolar segregation", although two other types of segregation, namely "united bipolar" (7%) and "separated bipolar" (12%) were also observed. After anaphase II, chromatids at the peripheral pole were released as polar body II (PB2). The release of two sets of chromatids as PB2 through either a united bipolar or a separated bipolar segregation resulted in the formation of meiosis I triploids (14%). The release of one set of chromatids as PB2 from an unmixed tripolar or a separated bipolar segregation formed meiosis I tetraploids (20%). Aneuploids (56%) were produced, primarily when the two groups of dyads from meiosis I united or overlapped before entering the tripolar segregation.

The value of hysteroscopy in the diagnosis of infertility and habitual abortion

Ninety cases of infertility and habitual abortion were analyzed by hysteroscopy between April 1983 and July 1990 in PUMC hospital. Abnormal changes of the uterine cavity were seen in 74.4%. The result of hysterosalpingography corresponded with that of hysteroscopy in 62.5%, and the result of B-ultrasound corresponded to that of hysteroscopy in 52.5%. The diagnosis of adhesion and polyps of the uterine cavity was made accurately by hysteroscopy, and both could be operated under hysteroscopy. After operative removal of the adhesion, an IUD should be put into the uterine cavity for 3 months. In 60 cases operations were performed during or after hysteroscopy. Of the 45 patients followed, 19 achieved pregnancy. Five patients achieved pregnancy after operative removal of the adhesion. It is concluded that hysteroscopy is more important than B-ultrasound and hysterosalpingography in the examination and treatment of infertility.

Stigmatic grazing-incidence flat-field grating spectrograph

A stigmatic grazing-incidence flat-field grating spectrograph was developed. The spectrograph consisted of a variable line-spacing concave grating and a grazing-incidence collecting optics composed of a cylindrical mirror and a spherical mirror. Using this spectrograph, we have obtained soft x-ray spectra of line-focused laser plasmas with good spatial resolution along the normal of the target surface over the entire wavelength range covered by the spectrograph.

Retinoma and phthisis bulbi of retinoblastoma. 1. Clinical and genetic analysis

Retinoma and phthisis bulbi of retinoblastoma are rare entities found in retinoblastoma patients and their relatives. Eleven cases of phthisis bulbi of retinoblastoma and 9 cases of retinoma were identified from 1966 to 1991 in our center. The clinic data show that retinoma and phthisis bulbi are closely related to the retinoblastoma gene. Enucleation should be carried out as soon as possible without hesitation for the phthisis of eyes with retinoblastoma. Genetic counseling and frequent observation should be paid attention to retinoma patients and their offspring. The mechanism of retinoma developed is discussed. We propose that the diversity of second mutation might be the cause of retinoma.

[Feed-back regulation of presynaptic D2 receptors blockaded by l-stepholidine and l-tetrahydropalmatine]

The activity of tyrosine hydroxylase by accumulation of L-dopa content in the striatum under decarboxylase inhibitor (benserazide, 400 mg.kg-1) was measured by HPLC-ECD to ascertain whether l-SPD possesses an agonistic or antagonistic effect on D2 receptor subtype. The accumulated L-dopa content was increased with 1,4-butyrolactone (BL, 750 mg.kg-1) to 1.8 +/- s 0.6 micrograms.g-1 in rat striatum. After the rats were ip l-SPD 5 mg.kg-1 or l-tetrahydropalmatine (l-THP) 10-20 mg.kg-1, the increment of L-dopa level was much more than that in the BL group (P < 0.01) in a dose related manner. On the contrary, apomorphine (ip 5 mg.kg-1) abolished the accumulation of L-dopa induced by BL. Furthermore, l-SPD and l-THP not only reversed the negative feed-back regulation by apomorphine on the accumulated level of L-dopa, but also increased this level over the accumulation by BL. These results showed that l-SPD and l-THP do possess the antagonistic effect on presynaptic DA receptor (D2) without agonistic effect.

Modern surgical treatment of congenital subluxated lenses

Traditional surgical management of subluxated lenses is usually associated with a high incidence of operative and postoperative complication and a poor visual outcome. We treated a series of 14 patients (26 eyes) whose visual acuity could not be improved with optical correction (phakic or aphakic) with modern microsurgery and automated suction-cutting devices. Preoperative visual acuity ranged from 0.05 to 0.3. Improvement in post-operative visual acuity was documented in all operated eyes, ranging from 0.4 to 1.0 during a follow-up period ranging from 6 to 59 months (medium 43 months). The only complication was a small accidental cut in the pupillary border in three eyes. Other complication did not occur.

Regulated temporal and spatial expression of the calcium-binding proteins calcyclin and OPN (osteopontin) in mouse tissues during pregnancy

In situ hybridization and northern/slot blot analyses were used to quantify the expression of calcyclin (2A9, 5B10), osteopontin (opn, secreted phosphoprotein, 2ar) and calmodulin mRNAs in mouse tissues that support pregnancy. High-to-moderate levels of the mRNAs of all three genes were detected at discrete locations in the uterus, decidua and placenta as a function of gestation time. Calmodulin expression was constant in these tissues; calcyclin mRNA was high during early pregnancy and declined after day 8-9 of gestation; and opn mRNA was undetectable before day 7, with maximal levels on days 9-12 in each of these tissues. Calcyclin, but not opn, expression was also observed in the chorioamnion after day 12. Calcyclin was expressed throughout the decidua on day 8 but became restricted to the primary (antimesometrial) decidual zone and decidua lateralis on day 9, and the decidua capsularis after day 9. By contrast, opn mRNA was localized on day 9 to the mesometrial triangle, which contains a large population of granulated metrial gland cells, and to the decidua basalis. These two genes may serve as markers for the two types of decidual tissue. We suggest that one function of OPN, which may be an indicator of cells in the decidua that have a bone marrow genealogy, is to mediate the flux of calcium from the maternal circulation to the developing embryo.

Effects of l-stepholidine on tyrosine hydroxylase activity in rat corpus striatum

l-Stepholidine (SPD) 2.5 and haloperidol (Hal) 1.0 mg.kg-1 ip increased rat striatal L-3,4-dihydroxyphenylalanine (DOPA) and 3,4-dihydroxyphenylacetic acid (DOPAC) accumulation induced by NSD 1015 (50 mg.kg-1, ip), a decarboxylase inhibitor. SPD (2.5 mg.kg-1, ip) did not alter but apomorphine (2.0 mg.kg-1, ip) decreased the dopamine (DA) content elevated by gamma-butyrolactone (GBL, 750 mg.kg-1, ip) in the rat striatum. Ip injection of either SPD 5.0 or Hal 2.5 mg.kg-1 after NSD 1015 50 mg.kg-1 or NSD 1015 plus GBL 750 mg.kg-1 also augmented tyrosine hydroxylase (TH) activity in the rat striatum. These results suggest that SPD produces an antagonistic effect on presynaptic DA receptors.

[Cytological observation on culture of embryo in vitro of Tripterygium hypoglaucum (level.) Hutch]

This paper for the first time reports the embryo culture in vitro of Tripterygium hypoglaucum. Callus, adventitious roots and adventitious protuberances were induced from the cultured embryos in vitro. Multi-buds at the excised embryo tip were also observed at the same time. Cytohistological examination showed (1) callus was histologically easy to be induced to form adventitious roots; (2) callus on the cotyledons was originated from the epidemical and subepidemical cells of the cotyledons, and the adventitious roots were originated from the disperse meristematic tissue or vascular tissue in the callus obtained from cultured excised embryos.

[Studies on second-degree atrioventricular block during atrial fibrillation]

The degree of AV block after cardioversion in 80 episodes of atrial fibrillation in 61 patients who suffered from atrial fibrillation associated with second-degree AV block was observed. Only in 34 of the 80 episodes the electrocardiogram showed first-degree AV block. The remaining 46 had normal AV conduction. No second-degree block was found. It demonstrates that second-degree AV block during atrial fibrillation is not identical with that in sinus rhythm.

[A clinical study and analysis of congenital lenticular dislocation (35 cases)]

Thirty-five cases of congenital lenticular dislocation seen in our Center since 1985 have been studied and analyzed clinically. By the survey of pedigrees and examination of these patients, including ocular, systemic, skeletal X-ray, psychocardiogram, and urinary sodium-nitroprusside test, 21 cases were diagnosed as Marfan's syndrome, 6 cases as simple ectopia lentis, 3 cases as Weill-Marchesani's syndrome, 4 cases as aniridia and 1 case as homecys tinuria. We found that the most significant ocular manifestation of congenital lenticular dislocation was reduction in visual acuity. The severity of visual disturbance varied with the types of dislocation and the visual deficiency was closely related to the intermediate-grade (II) dislocation of the lens. Examination of ERG showed normal function in most of the patients. From this, we believe that the major cause of visual reduction in congenital lenticular dislocation is lenticular myopia and astigmatism. There fore, early diagnosis and effective correction of vision should be emphasized to prevent the occurrence of amblyopia.

Studies on monoclonal antibody against recombinant human granulocyte colony-stimulating factor

Three hybridoma cell lines producing monoclonal antibodies (McAb) against recombinant human granulocyte colony-stimulating factor (rhG-CSF) have been established by fusing mouse myeloma cell line SP2/0 cells with spleen cells from a BALB/c mouse immunized with rhG-CSF. Ascites was obtained from BALB/c mice by injecting the hybridoma cells intraperitoneally. Three McAbs were purified by the caprylic acid-ammonium sulfate method. For each, the IgG subclass, valence and activity, molecular weight, specificity and affinity were determined. The applications of McAbs against rhG-CSF in the clinic and laboratory are discussed.

Acceleration sensitivity of crystal resonators affected by the mass and location of electrodes

Predominant thickness-shear frequencies and modes of a crystal plate with electrodes of arbitrary shape and mass distribution are obtained by a finite-element method, based on Mindlin's first-order equations with platings. These frequencies and modes are used in a perturbation method for computing the acceleration sensitivity of crystal resonators with electrodes. Computations are made for a square AT-cut quartz plate that is supported by a four-point mount and coated with identical square and uniform electrodes on the upper and lower faces of the plate. To study the effect of uneven distribution of electrode mass, acceleration sensitivities are calculated when a small mass is added at various locations near the edges of the square electrodes. It is found that the percent increase of the acceleration sensitivity of the resonator with a small added mass to that of the resonator without added mass ranges from 3.8% to 541.7%, depending on the location of the small mass placed at the edges of the electrodes.

Lappaconitine and N-deacetyllappaconitine potentiate footshock-induced analgesia in rats

The effects of lappaconitine (LA) and N-deacetyllappaconitine (DLA) on footshock-induced analgesia (FSIA) were studied by the rat tail flick test. Rats subjected to 90 s nonescaping footshock had a significant increase in tail flick latency. Naloxone (4 micrograms, i.c.v.) partially antagonized the FSIA. After 5 consecutive exposures to footshock, rats developed a complete tolerance to the FSIA. The rats tolerant to FSIA showed a cross-tolerance to morphine- but not LA- and DLA-induced analgesia. Administrations of subanalgesic doses of LA and DLA potentiated the FSIA in both intact and adrenalectomized rats.

[Primary study of iontophoresis of zinc ion in treatment of retinitis pigmentosa]

We report here the preliminary effects of zinc iontophoresis in treatment of 26 Rp patients who had decreased zinc serum level or abnormal ratio of serum copper to zinc. Through more than 20 to 30 times of therapy, the vision of 15.38% eyes increased more than "3 lines", 4% eyes increased more than 5 degrees in the visual field, 13.46% eyes improved in dark adaptation threshold (greater than 1.0), the visual functions of the rest eyes were slightly improved or unimproved. The fundus didn't change before & after treatment. There were no changes of ERG in 8 eyes of 4 cases. In addition, the advantages and disadvantages between Zn iontophoresis and Zn compound taken orally, the improvement of vision by direct electric current therapy, the relationship between the metabolism of Zn element and Vit A and influence of Zn over the mechanism of dark adaptation were also briefly discussed.

Roles of periaqueductal gray and nucleus raphe magnus on analgesia induced by lappaconitine, N-deacetyllappaconitine and morphine

In the rat tail flick test, ip LA 6 mg/kg, icv DLA 60 micrograms and icv or with morphine 5 micrograms exhibited significant analgesia. But with either LA 40 micrograms or DLA 60 micrograms was inactive. Naloxone (4 micrograms icv) which antagonized morphine analgesia failed to alter the analgesia induced by LA and DLA. Microinjection of DLA 20 micrograms or morphine 5 micrograms into the periaqueductal gray (PAG) or nucleus raphe magnus (NRM) produced markedly analgesic activity. The effects of electrolytic and kainic acid (0.8 micrograms) lesions of the PAG and NRM on the analgesia elicited in the rat from ip LA, icv DLA and morphine were also evaluated. No change in baseline tail flick latency was observed following lesions of the PAG and NRM. But lesions of the PAG and NRM significantly attenuated the analgesia mediated by LA, DLA and morphine. These results suggest that supraspinal sites, especially the PAG and NRM, are involved in the analgesic action induced by LA, DLA and morphine.

[Effects of reserpine and 5-HT on analgesia induced by lappaconitine and N-deacetyllappaconitine]

In the rat tail-flick test it was shown that ip lappaconitine (LA) 1-6 mg/kg, N-deacetyllappaconitine (DLA) 4-10 mg/kg or icv DLA 20-60 micrograms/rat exhibited a dose-dependent analgesic activity, but icv LA 20-40 micrograms/rat was inactive. The analgesic potency of ip LA was a little more potent than that of DLA and slightly weaker than that of morphine (P less than 0.05). Combined ip of subanalgesic doses of morphine and LA or DLA produced significant analgesic action. Analgesia mediated by LA was not antagonized by naloxone. The analgesic effect induced by LA or DLA was abolished and restored 3 and 120 h, respectively, after ip reserpine 3 mg/kg. Concomitant administration of 1-tryptophan or 5-HT as well as premedication of alpha-methyldopa prevented reserpine-induced decrease on LA or DLA analgesia. The elevation of brain 5-HT level by icv 5-HT significantly enhanced the analgesia of LA and DLA. LA- or DLA-induced analgesia was attenuated by pretreatment of p-chlorophenylalanine but this attenuation was reversed by icv 5-HT. p-Chloroamphetamine also markedly reduced LA- or DLA-induced analgesia. It is concluded that the central serotoninergic system is involved in the modulation of LA- or DLA-induced analgesia.

[Effects of central Ca2+ on analgesic action of lappaconitine]

Lappaconitine (LA), isolated from Aconitum sinomontanum Nakai, was characterized as analgesic principle by our laboratory. The analgesic effect of ip LA 6 mg/kg as measured in the rat tail-flick test was reduced by icv CaCl2 or MgCl2 0.1 or 1 mumol/rat. BaCl2 was inactive. The analgesic action induced by LA was potentiated by ethylene glycol tetraacetic acid (EGTA, 0.2 mumol/rat icv) but not by ethylenediamine tetraacetic acid (EDTA, 0.2 or 0.4 mumol/rat icv). The calcium antagonists nifedipine (5 mg/kg ip) and verapamil (1 mumol/rat icv) partially reversed the Ca2+ antagonistic effect on LA analgesia, although nifedipine did not enhance LA analgesic action and only at 15 min after medication did verapamil exhibit enhancement of LA analgesia. The analgesic activity of LA was reduced and augmented by microinjection of CaCl2 0.5 mumol and EGTA 50 nmol to periaqueductal gray (PAG) area, respectively. These results suggest that LA can produce analgesia, possibly through a decrease in cellular calcium availability and PAG may be involved in the Ca2+ antagonistic effect on LA analgesia.

Isochannels and blocking modes of voltage-dependent sodium channels

Our results support the existence of three different Na-channel subtypes or isochannels. These isochannels can be readily distinguished as the predominant Na-channel types in mammalian brain, skeletal muscle, and cardiac muscle. The sensitivity to mu-conotoxin GIIIA and tetrodotoxin is sufficient to classify these channels. The skeletal muscle channel is very sensitive to both tetrodotoxin and mu-conotoxin, the brain channel is sensitive to tetrodotoxin but insensitive to mu-conotoxin, and the heart and denervated muscle channels are insensitive to both toxins. In addition to block at the external receptor site for guanidinium toxins, several other blocking modes can be generalized for batrachotoxin-activated Na channels. One mode is peculiar to certain hydrophobic molecules so far represented by our studies of benzocaine and procaine. These molecules induce discrete blocking events with dwell times that apparently increase with anesthetic concentration and a blocking frequency that increases with negative voltage. This mode is quite distinct from the fast internal block by charged organic molecules that increases with positive voltage. These results imply that it is not possible to ascribe the diverse effects of local anesthetics to a single site in the interior channel mouth, as previously proposed by Hille. Our observations thus support the conclusions of other workers who used mixtures of two local anesthetics to show that the dose-response behavior does not fit single-site behavior, but requires at least two distinct sites. Two additional blocking modes can be distinguished for the interactions of cations at the internal and external mouths of the channel. Organic molecules can apparently enter the electric field from the internal but not the external side of the channel. This result suggests a wide internal entry way to the field and an external constriction that prevents the entry of molecules with a single methyl group but permits entry of divalent inorganic cations such as Ca2+ and Co2+.

Two-stage global search designs for linkage analysis using pairs of affected relatives

We investigate the two-stage procedure proposed by Elston [(1992) Proceedings of the XVIth International Biometric Conference, Hamilton, New Zealand, December 7-11, 1992, pp 39-51, and (1994) "Genetic Approaches to Mental Disorders." Washington, DC: American Psychiatric Press, pp 3-21] for performing a global search of the genome to locate disease genes by linkage analysis using affected relative pairs. The optimal design depends on the type of pairs studied, the effect of the disease locus, the relative costs of recruiting affected persons and typing markers, how informative the markers are, and the amount of genetic heterogeneity. It is specified by the initial number of markers to use, the number of affected relative pairs to study, the initial significance level alpha* to use at the first stage, and the number of flanking markers to use at the second stage around markers significant at the first stage. Asymptotically, the optimal design does not depend separately on either the desired final significance level or power, but rather on a function of the two. Both as the effect of the disease locus increases and as the relative cost of recruiting a subject increases, the optimal number of initial markers increases and the optimal number of pairs decreases. The expected cost of the study decreases as the effect of the disease locus increases, but increases as the relative cost of recruiting a subject increases. The optimal initial number of markers decreases but the number of pairs increases when there is genetic heterogeneity present; conversely, the optimal initial number of markers increases when markers are less than fully informative. Compared to a one-stage procedure, a two-stage procedure typically halves the cost of a study.