Surgical treatment for mild deformities of the rheumatoid forefoot by partial phalangectomy and syndactylization

Thirteen patients (14 feet) were treated for mild rheumatoid forefoot deformities with lesser toe partial proximal phalangectomies and partial syndactylizations. Eleven patients (85%) were reviewed at an average of 8 years postoperatively. The results were completely satisfactory in four patients, satisfactory with minor reservations in three patients, satisfactory with major reservations in one patient, and unsatisfactory in three patients. The major cause of reservations and lack of satisfaction was metatarsalgia. Seven patients (64%) reported that their activities were limited by intermittent metatarsalgia. Four patients (36%) considered the cosmetic appearance of the forefoot to be unsatisfactory. All but one patient required some form of shoewear modification. Based on this study, we believe the indications for this procedure are limited. These include rheumatoid patients with mild forefoot deformities without significant metatarsalgia or ongoing disease who have failed nonoperative treatment. Relative contraindications to this operation appear to include the recent onset of rheumatoid arthritis, active disease, significant metatarsalgia, and strong cosmetic concerns regarding outcome. In borderline clinical decisions that involve whether or not to leave or excise the lesser metatarsal heads, they probably should be excised to decrease late metatarsalgia.

Association between wild type and mutant APC gene products

Germline mutations of the APC gene are responsible for familial adenomatous polyposis, an autosomal dominant inherited predisposition to colorectal tumors. Mutation of the APC gene is also an early, if not initiating, event for sporadic colorectal tumorigenesis. In both cases, almost all of the currently identified mutations of APC result in the truncation of the protein. In this study, we demonstrate that truncated APC proteins can associate with the wild type APC in vivo. Using in vitro expression and immunoprecipitation, we show that the first 171 residues of APC are sufficient for APC oligomerization and that the first 45 amino acids of APC is necessary for this interaction. These results indicate that most mutant APC proteins should be able to bind to wild type APC protein and perhaps inactivate it in a dominant negative manner.

A motility in the eukaryotic flagellum unrelated to flagellar beating

We report a motility in the flagella of the green alga Chlamydomonas that is unrelated to dynein-based flagellar beating. This motility, referred to as intraflagellar transport, was observed as the rapid bidirectional movement of granule-like particles along the length of the flagella. Intraflagellar transport could be experimentally separated from other, previously reported, nonbeat flagellar motilities. EM of flagella showed groups of nonvesicular, lollipop-shaped structures positioned between the outer doublet microtubules and the flagellar membrane. Movement of these complexes along the length of the flagella may be responsible for intraflagellar transport.

Conformational coupling in DNA polymerase fidelity

The fidelity of DNA polymerases is largely attributable to a two-step nucleotide binding mechanism. In the first step, binding contacts are initially made between the template and the incoming dNTP. The selectivity of this ground-state binding is similar in magnitude to the selectivity seen in forming base pairs in solution. In the second step, a change in protein conformation occurs, which leads to rapid incorporation of the dNTP into the growing polymer. This conformational change appears to occur globally in that it is inhibited by mismatches in the dNTP or in any of the three terminal base pairs of the primer/template. The open conformation allows rapid binding of the dNTP from solution, while the closed conformation provides steric checks for the proper Watson-Crick base pair geometry. This conformational change accounts for the extraordinary fidelity of polymerization and also provides selectivity to the exonuclease by inhibiting polymerization over a mismatch in the primer/template. The overall fidelity approaches one error in 10(10) by a combination of selectivity in polymerization (10(5)-10(6)) and in proofreading (10(3)-10(4)). This paradigm provides the theoretical basis for further investigation of the structural basis for fidelity by pointing to the essential elements of the polymerization reaction that need to be examined in order to evaluate active-site-directed mutants of polymerases to test appropriate structure/function relationships.

Expression, purification, and characterization of the Drosophila kinesin motor domain produced in Escherichia coli

The Drosophila kinesin heavy-chain gene was truncated to obtain the N-terminal 401 amino acid motor domain (designated K401) containing both the microtubule and ATP binding sites. The plasmid construct with the truncated kinesin gene was used to transform Escherichia coli. After induction, K401 was expressed as soluble kinesin protein at high levels and purified to homogeneity in milligram quantities. The purified protein was active and behaved as native kinesin with respect to its steady-state kinetic properties: K401 demonstrated a very low ATPase activity (kcat = 0.01 s-1) which was stimulated approximately 1000-fold by the addition of microtubules (kcat = 10 s-1; K0.5,MT = 0.9 microM tubulin; Km,ATP = 31 microM). Like native kinesin, K401 when purified contained ADP tightly bound at its active site, and the release of ADP from the active site occurred at a rate equal to the steady-state ATPase kcat. Active-site measurements using [alpha-32P]ATP demonstrated a stoichiometry of one ATPase site per K401 molecule. Like native kinesin, K401 can also hydrolyze MgGTP, and in the presence of microtubules, the rate of hydrolysis was increased dramatically from 0.03 to 16 s-1 (K0.5,MT = 2 microM tubulin; Km,GTP = 3.5 mM). These results establish that an active kinesin motor domain can be bacterially expressed and that this domain, the N-terminal 401 amino acids of the Drosophila kinesin heavy chain without light chains or additional eukaryotic factors, has full catalytic activity with microtubules.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional cerebral blood flow improves with treatment in chronic cocaine polydrug users

Brain perfusion is abnormal in chronic cocaine users. To determine whether these perfusion abnormalities are reversible following treatment, we studied 10 cocaine-dependent polydrug users with 99mTc-HMPAO SPECT 2 to 3 days after admission to an inpatient treatment facility and at 7 to 8 days and 17 to 29 days after abstinence from drugs. The patients also received buprenorphine, an opioid mixed agonist-antagonist, beginning 10 days after admission and continuing to the end of the study. Imaging began 10-15 min after injection of 99mTc-HMPAO (20 mCi) using an annular gamma camera system. MRI was performed during hospitalization using a 1.5 Tesla system. SPECT and MRI were merged and five axial SPECT slices centered at the level of the basal ganglia were selected for analysis. Activity ratios were derived for cortical regions relative to cerebellar activity and were corrected for linearity with respect to regional cerebral blood flow. The cortical regions were classified as abnormal (activity ratio < 0.6), borderline (0.6-0.72) and normal (> 0.72) based on the results of the first SPECT study. In abnormal zones, regional cerebral blood flow (rCBF) increased 11.0% +/- 9.0% at 7 to 8 days and 23.8% +/- 9.4% at 17 to 29 days after initiation of treatment. The increase in rCBF was 4.8% +/- 7.1% (7 to 8 days) and 11.1% +/- 8.0% (17 to 29 days) in borderline cortex and decreased 2.9% +/- 6.3% (7 to 8 days) and increased only 2.7% +/- 13.4% (17 to 29 days) in normal cortex. The increase in rCBF did not vary significantly by location. The perfusion defects observed in chronic cocaine polydrug users are partially reversible with short-term abstinence and buprenorphine treatment.

Sprained ankles as they relate to the basketball player

Concepts based on newer medical information concerning ankle injuries have changed in recent years. With these changing concepts, the method of treatment has also changed. It is the purpose of this article to review some of the commonly known information concerning ankle sprains, to emphasize the association of subtalar injury with the ankle sprain complex, to outline new information concerning the static stabilizers on the lateral aspect of the ankle, and finally, to utilize this information in producing a rationale for a new type of surgical treatment for chronic instability of the ankle.

Protein tyrosine phosphatase 1B undergoes mitosis-specific phosphorylation on serine

We have investigated the regulation of protein tyrosine phosphatase 1B (PTP1B) through the cell cycle of HeLa cells. PTP1B from HeLa cells arrested in mitosis migrated more slowly during sodium dodecyl sulfate-polyacrylamide gel electrophoresis than did PTP1B from unsynchronized HeLa cells. To explore whether this mobility shift was caused by phosphorylation, PTP1B was immunoprecipitated from 32Pi-labeled unsynchronized and mitotic HeLa cells. PTP1B from mitotic cells incorporated significantly more 32Pi than did PTP1B from unsynchronized cells. Alkaline phosphatase treatment of mitotic HeLa cell lysates resulted in the conversion of PTP1B to its more rapidly migrating form, confirming that the mobility shift was a result of the mitotic phosphorylation. Phosphoamino acid analysis of PTP1B from mitotic cells revealed that PTP1B became phosphorylated on serine. Dephosphorylation of PTP1B occurred following the release of cells from nocodazole synchronization and was independent of new protein synthesis. This dephosphorylation was inhibited by okadaic acid, a potent inhibitor of types 1 and 2A serine/threonine phosphatases. The mitotic phosphorylation had no apparent effect on the activity of PTP1B as measured in in vitro phosphatase assays using 32P-labeled Raytide as substrate. p34cdc2 appears not to be the mitotic PTP1B kinase, as mapping experiments showed that this enzyme phosphorylated PTP1B on a site different from that on which it was phosphorylated in vivo. These observations suggest that PTP1B may be differentially regulated through the cell cycle.

The APC gene product in normal and tumor cells

The APC gene has been found to be mutated during the development of sporadic colorectal tumors as well as in the germ line of familial adenomatous polyposis patients. To facilitate the characterization of both normal and mutant APC protein, a series of monoclonal and polyclonal antibodies specific for the APC protein was produced. When lymphoblastoid cell lines derived from seven familial adenomatous polyposis patients with known mutations were analyzed by Western blot, an approximately 300-kDa protein corresponding to the predicted size of full-length APC was detected in all 7 cell lines. In addition, truncated APC proteins corresponding to the product of the known mutated alleles could be detected in 4 of the 7 lines. Similar analysis of 23 colon carcinoma and 9 adenoma cell lines revealed truncated proteins in 24 (75%) of the cell lines. Moreover, 26 (81%) of the colon tumor lines were totally devoid of the normal, full-length protein. In contrast, Western blot analysis of 40 cell lines derived from sporadic tumors of other organs detected only full-length APC. Immunohistochemical analysis of APC in normal colonic mucosa revealed cytoplasmic staining with more intense staining in the basolateral margins of the epithelial cell. This staining was markedly increased in the upper portions of the crypts, suggesting an increased level of expression with maturation. These studies provide some initial clues to the function of the cytoplasmic protein APC and demonstrate the feasibility of identifying APC mutations by direct analysis of the APC protein.

Decoration of the microtubule surface by one kinesin head per tubulin heterodimer

Kinesin, a microtubule-dependent ATPase, is believed to be involved in anterograde axonal transport. The kinesin head, which contains both microtubule and ATP binding sites, has the necessary components for the generation of force and motility. We have used saturation binding and electron microscopy to examine the interaction of the kinesin motor domain with the microtubule surface and found that binding saturated at one kinesin head per tubulin heterodimer. Both negative staining and cryo-electron microscopy revealed a regular pattern of kinesin bound to the microtubule surface, with an axial repeat of 8 nm. Optical diffraction analysis of decorated microtubules showed a strong layer-line at this spacing, confirming that one kinesin head binds per tubulin heterodimer. The addition of Mg-ATP to the microtubule-kinesin complex resulted in the complete dissociation of kinesin from the microtubule surface.

Neurotoxicity screening methods are sensitive to experimental history

Toxicity studies commonly include unavoidable environmental differences (experimental history) among test groups, such as chemical taste, odor and irritation. The influence of environmental variables on USEPA guideline neurotoxicity tests was evaluated using an environmental enrichment model. 6-week-old male Fischer 344 rats were housed for 13 weeks in pairs with access to an exercise wheel, trained to run on a rotating rod and handled frequently. Control animals were housed singly, lacked the exercise wheel and rotating rod training, and had only routine interaction with caretakers. At the end of 13 weeks, flash evoked potentials (FEPs), somatosensory evoked potentials (SEPs), auditory brainstem responses (ABRs), grip performance, motor activity (MA), elements of the functional observational battery (activity and reactivity to handling/restraint) and brain histopathology with glial fibrillary acidic protein immunohistochemistry (GFAP IHC) were evaluated. Animals from the enriched group demonstrated changes (P < 0.05) in FEPs, SEPs and grip performance. Enriched animals were more active and reactive to their surroundings, and were highly reactive to physical restraint. Control (unenriched) animals showed little to no exploratory behavior and were more tolerant of restraint. Differences in experimental history can be detected using elements of standard guideline tests and may confound interpretation of such data if not taken into consideration.

Mechanism and fidelity of HIV reverse transcriptase

We have examined the RNA-dependent and DNA-dependent polymerase and ribonuclease H catalytic activities of human immunodeficiency virus reverse transcriptase using rapid transient kinetic methods with defined synthetic 25/45-mer DNA/RNA and DNA/DNA primer/templates. The Kd value for interaction of the enzyme with duplex DNA was 4.7 nM, and the value for RNA/DNA heteroduplex was of similar magnitude. A pre-steady state burst of nucleoside triphosphate incorporation was observed for both DNA and RNA templates. Analysis of the dATP concentration dependence of the burst rate provided Kd values for dATP of 4 and 14 microM and maximum rates of single nucleotide incorporation, kpol, of 33 and 74 s-1, for DNA and RNA templates, respectively. Subsequent turnovers were limited by the rate of dissociation of the primer/template from the enzyme at rates of 0.18 and 0.06 s-1 for duplex DNA and RNA/DNA heteroduplex, respectively. Analysis of rates of DNA polymerization and RNA cleavage using the RNA template revealed that the two activities are independent of one another. The polymerization rate (4-70 s-1) was dependent on dATP concentration, whereas the RNA cleavage occurred at a constant rate of 10 s-1 over the 100-fold dATP concentration range (2-200 microM). Examination of the RNA cleavage products resulting from a single turnover indicates that the polymerase and ribonuclease domains of the enzyme are separated by a distance corresponding to 19 bases of RNA/DNA heteroduplex, consistent with the recently published crystal structure (Kohlstaedt, L. A., Wang, J., Friedman, J., Rice, P. A., and Steitz, T. A. (1992) Science 256, 1783-1790). Analysis of the kinetics of processive synthesis suggested that the initial binding of dNTP leads to a faster rate of dissociation of DNA from the enzyme. Further investigation supported a two-step dNTP binding mechanism with the formation of an initial E.DNA.dNTP complex followed by a more stable E'.DNA.dNTP complex. The Kd values for incorporation of incorrect nucleoside triphosphates opposite a DNA template thymidine were 1010 microM for dGTP, 1240 microM for dCTP, and 840 microM for dTTP. The corresponding maximum kpol rates were 4.8 s-1 for dGTP, 0.52 s-1 for dCTP, and 0.41 s-1 for dTTP. These values provide fidelity estimates of 1740 for discrimination against dGTP, 19,700 for dCTP, and 16,900 for dTTP misincorporations at this site.

Polarity of flagellar assembly in Chlamydomonas

During mating of the alga Chlamydomonas, two biflagellate cells fuse to form a single quadriflagellate cell that contains two nuclei and a common cytoplasm. We have used this cell fusion during mating to transfer unassembled flagellar components from the cytoplasm of one Chlamydomonas cell into that of another in order to study in vivo the polarity of flagellar assembly. In the first series of experiments, sites of tubulin addition onto elongating flagellar axonemes were determined. Donor cells that had two full-length flagella and were expressing an epitope-tagged alpha-tubulin construct were mated (fused) with recipient cells that had two half-length flagella. Outgrowth of the shorter pair of flagella followed, using a common pool of precursors that now included epitope-tagged tubulin, resulting in quadriflagellates with four full-length flagella. Immunofluorescence and immunoelectron microscopy using an antiepitope antibody showed that both the outer doublet and central pair microtubules of the recipient cells' flagellar axonemes elongate solely by addition of new subunits at their distal ends. In a separate series of experiments, the polarity of assembly of a class of axonemal microtubule-associated structures, the radial spokes, was determined. Wild-type donor cells that had two full-length, motile flagella were mated with paralyzed recipient cells that had two full-length, radial spokeless flagella. Within 90 min after cell fusion, the previously paralyzed flagella became motile. Immunofluorescence microscopy using specific antiradial spoke protein antisera showed that radial spoke proteins appeared first at the tips of spokeless axonemes and gradually assembled toward the bases. Together, these results suggest that both tubulin and radial spoke proteins are transported to the tip of the flagellum before their assembly into flagellar structure.

Dynamics of ribozyme binding of substrate revealed by fluorescence-detected stopped-flow methods

Fluorescence-detected stopped-flow and equilibrium methods have been used to study the mechanism for binding of pyrene (pyr)-labeled RNA oligomer substrates to the ribozyme (catalytic RNA) from Tetrahymena thermophila. The fluorescence of these substrates increases up to 25-fold on binding to the ribozyme. Stopped-flow experiments provide evidence that pyr experiences at least three different microenvironments during the binding process. A minimal mechanism is presented in which substrate initially base pairs to ribozyme and subsequently forms tertiary contacts in an RNA folding step. All four microscopic rate constants are measured for ribozyme binding of pyrCCUCU.

The effects of consultation on over-the-counter medication purchasing decisions

This article examines factors that predict changes in consumer purchasing decisions of nonprescription medications. Variables corresponding to factors in Andersen's behavioral model are measured, in addition to data regarding characteristics of the 17 pharmacy consultants who provided counseling services. One thousand seven hundred and thirteen consumers in five stores in southern California were provided consultation during a 6-month period, resulting in 25.4% of the patients purchasing a different drug than intended when entering the pharmacy, 1.3% being referred to a physician, and 13.4% not purchasing any over-the-counter medication at all. Logistic regression techniques demonstrated that one enabling variable (availability of generic medications), and four need factors (the discussion of clinical issues, short encounters, cough and cold products, and vitamin products) were significant predictors of the consumer's decision to purchase a different product than intended. Consultant characteristics (introversion, external locus of control) were also important predictors, but opposite the expected direction. Consumers who received information from female consultants were more likely to change their purchasing decisions.

Anaerobic bacteria isolated from osteomyelitis in dogs and cats

Anaerobic bacteria were isolated from 18 of 28 animals (64%) with osteomyelitis. The bones most commonly infected with anaerobic bacteria were radius and ulna, mandible, and tympanic bulla. Fights or abscesses commonly preceded the osteomyelitis. Seven anaerobic genera were isolated. Mixed infections of anaerobic and aerobic organisms occurred in 16 animals. Staphylococci were isolated in only one such mixed infection, but they were isolated commonly when there were aerobic bacteria only. Staphylococcal infections were often single.

Fetal alcohol syndrome: a case report of neuropsychological, MRI and EEG assessment of two children

Neuropsychological, neuroanatomical, and electrophysiological data are presented on two subjects with fetal alcohol syndrome (FAS). Both boys had intelligence quotients in the mentally deficient range and were found to have several other severe, specific deficits. Magnetic resonance imaging showed abnormalities of the corpus callosum, and reductions in the size of the basal ganglia and thalamic structures. No focal abnormalities were noted in the electroencephalogram records, although the electroencephalograms of both boys were moderately abnormal for their age group. A multidisciplinary approach to the study of FAS, hopefully will lead to a more unified concept of the disorder and perhaps indicate specific areas of vulnerability.

Correction of cervical esophageal stricture in a dog by creation of a traction diverticulum

A cervical esophageal stricture was corrected in a dog by creation of a traction diverticulum. Although abnormal esophageal motility persisted in the portion of the esophagus cranial to the stricture, the clinical effects of the stricture were ameliorated by the simple surgical procedure.

Maintenance energy requirement of llamas

Five castrated male llamas (mean body weight, 94 kg) were studied in an energy balance trial to determine maintenance energy requirement of llamas. Llamas were fed a 50% oat hay-50% pelleted concentrate diet (2.43 Mcal of metabolizable energy/kg of diet dry matter) at approximately 1.6% of body weight (BW). An 8-day total collection digestion trial was used to determine fecal and urine energy losses. Heat production and methane emissions were determined via indirect respiration calorimetry measurements on each llama fed at the same level of intake as during the digestion trial and subsequently on days 3 and 4 of a period of nonfeeding. Fecal, urine, and methane energy losses of the llamas fed near-maintenance intake were 32.5, 3.5, and 7.1% of gross energy intake, respectively. The postabsorptive metabolic rate, commonly called nonfed (fasting) heat production, was 59.3 kcal/BW0.75. Using a linear relation between postabsorptive and maintenance energy requirement and efficiency of energy use below maintenance of 0.702, metabolizable energy requirement at maintenance was determined to be 84.5 kcal/BW0.75.

Cloning and expression of gene 4 of bacteriophage T7 and creation and analysis of T7 mutants lacking the 4A primase/helicase or the 4B helicase

T7 gene 4, which is required for DNA replication, specifies two proteins whose coding sequences overlap in the same reading frame: the 4A protein, a 566-amino acid primase/helicase, and the 4B protein, a 503-amino acid helicase whose initiation codon is the 64th codon of the 4A protein. To study better the individual functions of these two overlapping proteins, we made clones that express both 4A and 4B proteins, only 4B protein, or only what we refer to as the 4A' protein, in which methionine 64 is replaced by leucine, thereby eliminating the 4B initiation codon. These clones provide considerably more gene 4 protein for biochemical analysis than do infected cells. They can also be used to isolate and propagate T7 gene 4 deletion mutants, and we have made T7 mutants which lack all gene 4 coding sequences, or which express 4A' protein but no 4B protein, or 4B protein but no 4A protein. Analysis of these phage mutants shows that 4A' protein without any 4B protein can support essentially normal replication and growth, whereas 4B protein without any 4A protein supports little replication or growth. Apparently, the primase activity of the 4A protein is essential for replication, but the 4B protein is dispensable, presumably because the 4A protein also supplies helicase activity. The mutation at amino acid 64 of 4A' appears to have little effect on 4A function. The rate of replication during normal T7 infection appears to be limited by the amount of gene 4 protein, but too high a level of either 4A or 4B protein is inhibitory to growth.

Large scale purification and biochemical characterization of T7 primase/helicase proteins. Evidence for homodimer and heterodimer formation

A rapid purification procedure produces milligram amounts of the T7 gene 4A' primase/helicase, 4B helicase, and the wild-type 4AB proteins expressed from the clones described in the accompanying paper (Rosenberg, A. H., Patel, S. S., Johnson, K. A., and Studier, F. W. (1992) J. Biol. Chem. 267, 15005-15012). Purified 4A' protein (in which the wild-type methionine at amino acid 64 has been replaced by leucine to eliminate the 4B initiation codon) appears to be equivalent to the wild-type 4A protein in primase, helicase, and NTPase activities. Gel filtration chromatography and polyacrylamide gel electrophoresis of native proteins indicate that the 4A' and 4B proteins form homodimers and heterodimers in solution. Heterodimer formation presumably accounts for an observed 3-fold increase in the primase activity of 4A' upon addition of 4B that lacks primase activity of its own. Steady-state k(cat) and Km values for hydrolysis of the nucleoside triphosphates ATP, dATP, dTTP, and dGTP were measured for 4A', 4B, 4A'B (1:1), and wild-type 4AB (1:2) proteins. The dependence of the dNTPase activities on the concentration was hyperbolic, suggesting single or noncooperative binding sites, whereas ATPase activity was sigmoidal, suggesting more than one ATP binding site. The k(cat)/Km ratios for hydrolysis of the dNTPs by the four protein preparations were within a factor of 6 of each other. The 1:1 mixture of 4A'B had the highest k(cat)/Km ratios, with a preference for dATP and dTTP.

A comparison of brain perfusion SPECT in cocaine abuse and AIDS dementia complex

Intravenous drug use is a major risk factor for HIV-1 infection. Since both AIDS dementia complex (ADC) and cocaine have been associated with abnormal brain perfusion imaging, we compared the scintigraphic patterns of ADC patients and cocaine polydrug users with normal control subjects using 99mTc-HMPAO SPECT. We found a high incidence of cortical defects in both ADC (100%) and cocaine-dependent (90%) subjects. In the cocaine and ADC patients, cortical defects were most frequent in the frontal, temporal and parietal lobes and occurred with similar frequency in the two populations. In both groups, the number of cortical defects per subject was higher than normal subjects (10.0 +/- 5.0 for ADC, 10.1 +/- 5.2 for cocaine and 0.7 +/- 1.5 for normal), background activity was high (a 65% and 60% incidence for ADC and cocaine, respectively), and basal ganglia involvement was frequent (40% and 65% for ADC and cocaine). We conclude that the brain perfusion pattern, while a sensitive indicator of ADC, cannot be distinguished from chronic cocaine polydrug use and caution should therefore be applied before entertaining a specific diagnosis.

Molecular analysis of the Neurospora clock: cloning and characterization of the frequency and period-4 genes

Genetic analysis of Neurospora crassa has identified many mutants that affect the biological clock. In this article we review the cloning of two of these genes, frq and prd-4. Both genes were isolated using a chromosome walk technique. Subcloning experiments and subsequent Northern analysis of frq implicate the importance of two transcripts that emanate from this locus. In preliminary data, no protein-coding region is evident in the smaller transcript; the larger transcript contains a 962-amino acid open reading frame. The open reading frame shows limited homology to per, a clock gene identified in Drosophila. Sequence analysis of all existing frq alleles suggests that the defect in each case lies within the open reading frame. Successful cloning of the prd-4 gene required walking a distance of greater than 40 kb. A physical map of this region has been constructed using restriction analysis. The dominance-recessive relationship of prd-4 and prd-4+ was established by examining the period lengths of strains harboring a wide range of prd-4/prd-4+ nuclear ratios.