Quality assessment of selected co-trimoxazole suspension brands marketed in Nairobi County, Kenya

INTRODUCTION

Quality of medicines in both developed and developing countries is sometimes compromised due to infiltration of counterfeit, substandard or degraded medicines into the markets. It is a public health concern as poor quality medicines endanger public health where patients are exposed to chemical toxins and/or sub-therapeutic doses. This could lead to reduced treatment efficacy and promote development of drug resistance. Co-trimoxazole, a fixed dose combination of sulfamethoxazole and trimethoprim, is a broad spectrum for bacterial diseases and is also used as a prophylaxis for opportunistic infections in HIV infected individuals. This study evaluated quality of selected co-trimoxazole suspension brands marketed in Nairobi County, Kenya.

METHODS

A total of 106 samples were collected, categorized into 15 brands and evaluated for active pharmaceutical ingredient content (API) and pH following United States Pharmacopeia. Assay for API was conducted using High Performance Liquid Chromatography. Results were compared with pharmacopeia references. Visual examination of labels and confirmation of retention status of the brands with Pharmacy and Poisons Board retention register was carried out.

RESULTS

The samples were primarily of local origin (86.7%). On October 23, 2019, retention status of six of the fifteen brands documented were no longer listed in the Pharmacy and Poisons Board retention register. Of the 106 samples tested 70.6% and 86.8% were compliant with United States Pharmacopeia (USP) specifications for pH and API respectively while 84.0% adhered to packaging and labelling requirements.

CONCLUSION

This study has demonstrated that majority of co-trimoxazole suspensions tested were compliant with USP requirements. Additionally, it has provided evidence of poor quality co-trimoxazole medicines that could compromise treatment of infectious diseases in children. This emphasizes the need for regular quality assurance tests to ensure only quality medicines are in the market.

Validity of caregivers' reports on prior use of antibacterials in children under five years presenting to health facilities in Gulu, northern Uganda

INTRODUCTION

Given the frequent initiation of antibacterial treatment at home by caregivers of children under five years in low-income countries, there is a need to find out whether caregivers' reports of prior antibacterial intake by their children before being brought to the healthcare facility are accurate. The aim of this study was to describe and validate caregivers' reported use of antibacterials by their children prior to seeking care at the healthcare facility.

METHODS

A cross sectional study was conducted among children under five years seeking care at healthcare facilities in Gulu district, northern Uganda. Using a researcher administered questionnaire, data were obtained from caregivers regarding reported prior antibacterial intake in their children. These reports were validated by comparing them to common antibacterial agents detected in blood and urine samples from the children using liquid chromatography with tandem mass spectrometry (LC-MS/MS) methods.

RESULTS

A total of 355 study participants had a complete set of data on prior antibacterial use collected using both self-report and LC-MS/MS. Of the caregivers, 14.4% (51/355, CI: 10.9-18.5%) reported giving children antibacterials prior to visiting the healthcare facility. However, LC-MS/MS detected antibacterials in blood and urine samples in 63.7% (226/355, CI: 58.4-68.7%) of the children. The most common antibacterials detected from the laboratory analysis were cotrimoxazole (29%, 103/355), ciprofloxacin (13%, 46/355), and metronidazole (9.9%, 35/355). The sensitivity, specificity, positive predictive value (PPV), negative predictive value and agreement of self-reported antibacterial intake prior to healthcare facility visit were 17.3% (12.6-22.8), 90.7% (84.3-95.1), 76.5% (62.5-87.2), 38.5% (33.0-44.2) and 43.9% (k 0.06) respectively.

CONCLUSION

There is low validity of caregivers' reports on prior intake of antibacterials by these children. There is need for further research to understand the factors associated with under reporting of prior antibacterial use.

In-vitro evaluation of the quality of paracetamol and co-trimoxazole tablets used in Malawi based on pharmacopoeial standards

OBJECTIVES

This study was an in-vitro evaluation of different brands of paracetamol and cotrimoxazole tablets, used or found in Malawi, based on Pharmacopoeia standards, in order to ascertain the existence and extent of substandard medicines in Malawi and to give an overview of their distribution in the public and private sectors.

METHODOLOGY

A cross-sectional analytical study was conducted using 11 samples each of paracetamol and cotrimoxazole tablets. Stratified random sampling was used to collect samples. Samples were analyzed using HPLC and Spectrophometric methods as outlined in the BP-2007 and USP-32 at the National Drug Quality Control Laboratory (NDQCL)-Lilongwe (under Pharmacy Medicines and Poisons Board-PMPB) and Orient Pharma Co. Ltd of Taiwan. The results were analyzed using Epi Info.

RESULTS AND DISCUSSION

Fifty percent of samples (n=22) were not registered in the country by the PMPB as required by the PMP Act with the majority of those coming from public health facilities. All paracetamol and cotrimoxazole samples complied with identification tests using spectrophotometric and HPLC method. Overall, 27.3% of samples failed to meet the BP-2007 standards for Active Ingredient content, while 22.7% of the samples failed the Friability test. The results from Malawi are similar in magnitude to those within surrounding countries in Africa.

CONCLUSION

This pilot study provides objective evidence to show that substandard and unregistered paracetamol and cotrimoxazole are present and being used in Malawi, and thus posing a considerable hazard to public health in Malawi. PMPB, together with the Ministry of Health, must continue to develop a quality assurance system to ensure that medicines are randomly and routinely checked.

Amoxicillin-clavulanic acid and trimethoprim- sulfamethoxazole in rodent feed and water: effects of compounding on antibiotic stability

We assessed the concentrations of 2 antibiotic combinations, amoxicillin-clavulanic acid and trimethoprim-sulfamethoxazole when compounded in reverse osmosis [RO] (pH 6.0), tap (pH 6.7), and acidified water (pH 2.6) over 7 d, and pre- and post-pelleting, post-gamma irradiation and shipping, and monthly until 180 d post-milling in feed. Amoxicillin concentrations in RO and tap water varied between 1.18 and 1.29 mg/ml, and 1.09 and 1.22 mg/ml, respectively. The concentration of amoxicillin declined immediately and remained between 0.43 and 0.50 mg/ml in acidified water. Clavulanic acid exhibited a slow time-dependent decrease in concentration to 0.05 mg/ml at day 7 in RO water, immediately declined and varied from 0.02 to 0.05 mg/ml in tap water, and was undetectable in acidified water. Trimethoprim and sulfamethoxazole concentrations were near expected in RO, tap, and acidified water. In food, amoxicillin, trimethoprim, and sulfamethoxazole concentrations were each reduced to approximately 60% of expected after pelleting, but remained stable thereafter for 180 d. The initial clavulanic acid concentration in feed was less than 10% of expected and was undetectable after 1 mo. Plasma drug concentrations were determined in C57BL/6NCrl mice at 4 h after commencement of the dark and light cycles following administration of antibiotic food for at least 72 h. Plasma amoxicillin and sulfamethoxazole concentrations were 3- and 10-fold greater, respectively, during the dark period. Plasma levels of clavulanic acid and trimethoprim were consistent at both time points. These results indicate that the antibiotic concentration can be influenced by compounding in feed and water, and differs in plasma during the light and dark phases of the photoperiod.

Simultaneous determination of trimethoprim and sulphamethoxazole in veterinary formulations by chromatographic multivariate methods

A comparative chromatographic study was developed for the simultaneous quantitative resolution of trimethoprim (TMP) and sulphamethoxazole (SMX) in veterinary formulations. Multi-wavelength chromatograms were recorded by using diode array detector (DAD) system at the five-wavelength set consisting of 220, 230, 240, 250 and 260 nm. In the first step, five different calibration equations at the above wavelengths for each drug were obtained by using the relationship between concentration and peak area. These calibration graphs were used for the quantitative evaluation of TMP and SMX in samples. These single-wavelength applications were called traditional LC method. In the second step, principal component regression (PCR) and partial least-squares (PLS) calibrations were applied to the above mentioned multi-wavelength chromatograms. The amount of two investigated drugs in samples was determined by the constructed PCR and PLS calibrations. The experimental results obtained from each single-wavelength calibration graph were compared with those obtained by the chemometric approaches and chromatographic multivariate approaches give successful results more than traditional LC method.

Enhanced stability of sulfamethoxazole and trimethoprim against oxidation using hydroxypropyl-beta-cyclodextrin

The effect of hydroxypropyl-beta-cyclodextrin (HPbetaCD) on the chemical stability of sulfamethoxazole and trimethoprim (co-trimoxazole) under oxidation stress at 50 +/- 2 degrees C was investigated. The concentrations of sulfamethoxazole and trimethoprim in aqueous solutions (pH 5.4) containing 0, 1%, 2%, 5%, 10% and 15% w/v hydroxypropyl-beta-cyclodextrin were measured by HPLC. Both sulfamethoxazole and trimethoprim degradation appeared to follow pseudo-first order kinetics in the presence and in the absence of hydroxypropyl-beta-cyclodextrin. The observed half-lives for sulfamethoxazole and trimethoprim in 15% w/v hydroxypropyl-beta-cyclodextrin were 910 h and 609 h respectively, 11.8 and 3.4 times greater than in solutions without hydroxypropyl-beta-cyclodextrin. Using a Lineweaver-Burk equation, the half-lives for sulfamethoxazole and trimethoprim outside the complex in a solution containing 15% w/v hydroxypropyl-beta-cyclodextrin were estimated at 77 h and 193 h respectively, whereas inside the complex the half-lives were estimated at 850 h and 821 h. In terms of relative increases in stability under oxidation stress the half-lives for sulfamethoxazole and trimethoprim inside the complex were 11.0 times and 4.2 times greater than their half-lives outside the complex. In conclusion, chemical stability of sulfamethoxazole and trimethoprim in co-trimoxazole aqueous solutions under oxidation stress at 50 +/- 2 degrees C can be increased using hydroxypropyl-beta-cyclodextrin as a molecular inclusion excipient.

Automated simultaneous triple dissolution profiles of two drugs, sulphamethoxazole-trimethoprim and hydrochlorothiazide-captopril in solid oral dosage forms by a multicommutation flow-assembly and derivative spectrophotometry

This article deals with the simultaneous determination of three dissolution profiles with the aid of the new and emerging continuous-flow methodology known as multicommutation. This methodology is based on a flow network of a set of solenoid valves controlled by the computer and acting as independent multicommutators to allow the easy and automated control of flowing solutions. The obtained three dissolution profiles from one dosage form are the whole formulation profile or "global profile" recommended by pharmacopoeias, and, at same time, are recorded two "individual" profiles from two drugs present in the formulation. This is the second attempt to obtain simultaneously three dissolution profiles with a single spectrophotometric detector and the first with the multicommutation methodology. The selected pharmaceutical formulations contained a couple of active principles with overlapped spectra, namely sulphamethoxazole and trimethoprim or hydrochlorothiazide and captopril. The obtained empirical plots profiles fitted with the Higuchi equation also known as the three-parameter equation.

The optimum pH for the derivative spectrophotometric determination of co-trimoxazole in binary mixtures

BACKGROUND

Although the experimental assessment of co-trimoxazole by use of derivative spectrophotmetry underscores the usefulness of this method due to its relative simplicity with which it can be carried out over the official United States Pharmacopoeia (USP) high pressure liquid chromatography (hplc) methods for this drug, suitable optimum conditions ought to be refined for its universal acceptability.

OBJECTIVE

The objective of the present work was to obtain the optimum pH level for the UV assessment of co-trimoxazole.

METHODS

The aqueous solutions of the individual drugs and their binary mixtures were buffered with Sodium Acetate-Acetic Acid buffer in the pH ranges 2-7 and scanned on zero order and on first-order derivative at the wave length between 200- 300 nm.

RESULTS

At the same drug solution concentrations, spectral shifts occurred with change in pH, especially between the wavelengths 200 and 240 nm, only seeming to converge from approximate wavelength 260 nm onwards. Absorbance fluctuations were also observed at the same drug concentrations in the pH range 2 to 3.5 and 5 to 7 when the solutions were scanned, even at the wavelength where the spectra seem to converge. However there were no absorbance differences between pH 4 and 5.

CONCLUSION

The UV spectrophotometric method is dependent on the optimum pH and this has been found to range from 4 to 5.

Simultaneous determination of binary mixtures of trimethoprim and sulfamethoxazole or sulphamethoxypyridazine by the bivariate calibration spectrophotometric method

The bivariate calibration algorithm was applied to the spectrophotometric simultaneous determination of trimethoprim (TMP), sulfamethoxazole (SMX) or sulphamethoxypyridazine (SMP) binary mixtures in pharmaceutical and veterinary products. The results obtained were compared with those from derivative spectrophotometry. The statistical evaluation of the method bias showed that the proposed procedure is comparable with commonly used first-derivative spectrophotometry. However, the advantage of bivariate calibration is its simplicity, due to the minimal spectra manipulation when compared with derivative techniques.

Indirect potentiometric titration of sulphamethoxazole in the presence of trimethoprim in co-trimazole tablets using copper based mercury film electrode

A simple and rapid indirect potentiometric titration of sulphamethoxazole in the presence of trimethoprim contained in co-trimazole tablets is described. The method is based on the formation of a complex of sulphamethoxazole with a known excess of silver ions and the titration of unreacted silver ion potentiometrically using an inexpensive lab-made copper based mercury film electrode (CBMFE). The titration conditions have been optimized for the determination of 1.0-10.0 mg of sulphamethoxazole in pure and dosage forms. The precision and accuracy of the method have been assessed by the application of lack of fit test and other statistical methods. Overall mean recovery and relative standard deviations obtained were 99.88% and 1.32% (n=7) respectively. No interference was caused by other excipients present in pharmaceutical dosage forms. The application of this method for sulphamethoxazole assay in the presence of trimethoprim in tablets was validated by the comparison of results obtained by the proposed method with that of the British Pharmacopoeia (BP) method using F- and t-statistical tests of significance.

Determination of the minor component bromhexine in cotrimoxazole-containing tablets by absorption spectrophotometry and partial least-squares (PLS-1) multivariate calibration

The mucolitic bromhexine [N-(2-amino-3,5-dibromobenzyl)-N-methylcyclohexylamine] has been determined in cotrimoxazole-containing tablets by partial least-squares (PLS-1) multivariate of spectrophotometric calibration data in the spectral range 310-350 nm. In the studied commercial tablets, cotrimoxazole is present in large excess (ca. 100:1 in weight) with respect to bromhexine, and a high degree of spectral overlapping exists among bromhexine and cotrimoxazole components. However, the obtained recoveries are reasonably good with the presently discussed technique.

The dissolution kinetics of sulfamethoxazol, trimethoprim and oxytetracycline hydrochloride from multicomponent solid dispersion capsules ("Sulfoxytrim")

Release profiles and dissolution kinetics of active substance, viz. sulfamethoxazol (SMO), trimethoprim (TMP), and oxytetracycline hydrochloride (OTC) from capsulated multicomponent dispersions was studied in a flow-cell apparatus at 37 degrees C by using a dissolution medium of 0.1 mol/l HCl. The results revealed that the relative dissolution efficiency (DE) and dissolution profiles of one active ingredient were affected by the presence of the two others. Vitamin C added caused the decreased the dissolution rate constants (K) and DE--values of all the active substances studied.

Biparental inheritance of gamma-tubulin during human fertilization: molecular reconstitution of functional zygotic centrosomes in inseminated human oocytes and in cell-free extracts nucleated by human sperm

Human sperm centrosome reconstitution and the parental contributions to the zygotic centrosome are examined in mammalian zygotes and after exposure of spermatozoa to Xenopus laevis cell-free extracts. The presence and inheritance of the conserved centrosomal constituents gamma-tubulin, centrin, and MPM-2 (which detects phosphorylated epitopes) are traced, as is the sperm microtubule-nucleating capability on reconstituted centrosomes. gamma-Tubulin is biparentally inherited in humans (maternal >> than paternal): Western blots detect the presence of paternal gamma-tubulin. Recruitment of maternal gamma-tubulin to the sperm centrosome occurs after sperm incorporation in vivo or exposure to cell-free extract, especially after sperm "priming" induced by disulfide bond reduction. Centrin is found in the proximal sperm centrosomal region, demonstrates expected calcium sensitivity, but appears absent from the zygotic centrosome after sperm incorporation or exposure to extracts. Sperm centrosome phosphorylation is detected after exposure of primed sperm to egg extracts as well as during the early stages of sperm incorporation after fertilization. Finally, centrosome reconstitution in cell-free extracts permits sperm aster microtubule assembly in vitro. Collectively, these results support a model of a blended zygotic centrosome composed of maternal constituents attracted to an introduced paternal template after insemination.

An essential role for katanin in severing microtubules in the neuron

Several lines of evidence suggest that microtubules are nucleated at the neuronal centrosome, and then released for transport into axons and dendrites. Here we sought to determine whether the microtubule-severing protein known as katanin mediates microtubule release from the neuronal centrosome. Immunomicroscopic analyses on cultured sympathetic neurons show that katanin is present at the centrosome, but is also widely distributed throughout the neuron. Microinjection of an antibody that inactivates katanin results in a dramatic accumulation of microtubules at the centrosome, indicating that katanin is indeed required for microtubule release from the centrosome. However, the antibody also causes an inhibition of axon outgrowth that is more immediate than expected on this basis alone. It may be that katanin severs microtubules throughout the cell body to keep them sufficiently short to be efficiently transported into developing processes. Consistent with this idea, there were significantly fewer free ends of microtubules in the cell bodies of neurons that had been injected with the katanin antibody compared with controls. These results indicate that microtubule-severing by katanin is essential for releasing microtubules from the neuronal centrosome, and also for regulating the length of the microtubules after their release.

Alignment of centrosomal and growth axes is a late event during polarization of Pelvetia compressa zygotes

Zygotes and embryos of the fucoid brown alga Pelvetia compressa undergo a series of asymmetric cleavages. We are interested in the developmental role of these cleavages and the mechanism controlling their alignment. To assess the importance of division plane alignment, the orientation of the first asymmetric division was altered and the effects on subsequent embryo elongation rates were analyzed. Although this division is normally oriented transversely (90 degrees) to the growth axis, deviations up to 45 degrees had no significant effects on embryo elongation. However, division planes that were parallel with the growth axis (0-45 degrees) had drastic effects. Embryo elongation was severely inhibited and the wall often bifurcated and avoided the rhizoid tip. The orientation of the division plane is determined by the position of the centrosomes. We therefore investigated centrosomal position and function during the first cell cycle within the three-dimensional context of the cell. We found that, after karyogamy, microtubule organization changed from a radially symmetric circumnuclear array into a bipolar centrosomal array. The reorganization coincided with the migration of the centrosomes around the nucleus. The centrosomes separated slowly and asynchronously until they reached opposite sides of the nuclear envelope. At this time the centrosomal axis, defined by the position of the two centrosomes, was oriented randomly with respect to the cortical growth axis. The centrosomal axis then rotated into alignment parallel with the growth axis late in the first cell cycle. These results indicate that the growth axis and the centrosomal axis develop independently of each other and that the centrosomal axis does not align with the growth axis until just prior to mitosis.

[Demonstration of two trimethoprim/sulfonamide combinations in bronchoalveolar lavage fluid of horses and determination of blood levels]

Five healthy horses were given a sulfadoxine/trimethoprim combination (Borgal, Hoechst AG) i.v. on day 1. The next ten days the horses got once a day a sulfadimethoxine/trimethoprim combination orally (Trafigal, Hoechst AG). The doses were given as recommended. One horse received no medicaments for control. On each horse six bronchoalveolar lavages were performed. Blood samples were taken to calculate blood levels and elimination half lives. To determine the amount of substances in lavage fluid and plasma the high performance liquid chromatography (HPLC) was used. Regularly low quantities of sulfonamides and trimethoprim were detected in lavage-samples. The mean plasma concentration (n = 4) of sulfadoxine and trimethoprim 30 min after i.v. administration was 71.6 and 1.13 micrograms/g respectively. 24 h after injection the sulfadoxine blood level was 3.0 micrograms/g, while trimethoprim was no longer detectable. The average elimination half lives of sulfadoxine and trimethoprim were 7.94 h and 1.35 h respectively. 8 h after oral application (n = 5) the highest mean sulfadimethoxine blood levels of 53.8 micrograms/g were measured. The elimination half life of sulfadimethoxine was 9.77 h. Two hours after feeding the drug the first blood samples were taken. They already contained the highest mean trimethoprim concentration of 0.32 microgram/g plasma.

Microtubule nucleation and release from the neuronal centrosome

We have proposed that microtubules (MTs) destined for axons and dendrites are nucleated at the centrosome within the cell body of the neuron, and are then released for translocation into these neurites (Baas, P. W., and H. C. Joshi. 1992. J. Cell Biol. 119:171-178). In the present study, we have tested the capacity of the neuronal centrosome to act as a generator of MTs for relocation into other regions of the neuron. In cultured sympathetic neurons undergoing active axonal outgrowth, MTs are present throughout the cell body including the region around the centrosome, but very few (< 10) are directly attached to the centrosome. These results indicate either that the neuronal centrosome is relatively inactive with regard to MT nucleation, or that most of the MTs nucleated at the centrosome are rapidly released. Treatment for 6 h with 10 micrograms/ml nocodazole results in the depolymerization of greater than 97% of the MT polymer in the cell body. Within 5 min after removal of the drug, hundreds of MTs have assembled in the region of the centrosome, and most of these MTs are clearly attached to the centrosome. A portion of the MTs are not attached to the centrosome, but are aligned side-by-side with the attached MTs, suggesting that the unattached MTs were released from the centrosome after nucleation. In addition, unattached MTs are present in the cell body at decreasing levels with increasing distance from the centrosome. By 30 min, the MT array of the cell body is indistinguishable from that of controls. The number of MTs attached to the centrosome is once again diminished to fewer than 10, suggesting that the hundreds of MTs nucleated from the centrosome after 5 min were subsequently released and translocated away from the centrosome. These results indicate that the neuronal centrosome is a highly potent MT-nucleating structure, and provide strong indirect evidence that MTs nucleated from the centrosome are released for translocation into other regions of the neuron.

Co-trimoxazole impairs colonization resistance in healthy volunteers

The influence of co-trimoxazole on colonization resistance of the bowel was investigated in six healthy volunteers, by measuring the numbers of indigenous aerobic flora and of a co-trimoxazole resistant challenge strain of Klebsiella pneumoniae. Impairment of colonization resistance of the bowel was shown by a significant increase in the numbers of yeasts in the faeces of five of six volunteers, by a significant increase in the numbers of Gram-negative bacilli in the faeces of two of six volunteers, and by facilitation of colonization of the bowel by the challenge strain in all volunteers. Impairment of colonization resistance of the mouth was shown by the development of glossitis caused by Candida albicans in two volunteers, and by a significant increase in the numbers of yeasts in mouth washings from four volunteers. It is concluded that co-trimoxazole impairs colonization resistance of the gastro-intestinal tract.

Centrin is a component of the pericentriolar lattice

Here, we use three polyclonal anticentrin antisera designated 08/28, 26/14-1, and 26/14-2 to further characterize the pericentriolar lattice of metazoan cells. All of these antibodies give an indistinguishable localization pattern that consists of a constellation of pericentrosomal spots. In QT6 cells these spots are few in number and closely associated with the centriolar region, whereas in PtK2 cells they are more numerous and distributed further from the point of microtubule focus. In mitotic cells, centrin is localized to the spindle poles and spindle apparatus. We demonstrate here that the pericentriolar lattice of PtK2 and QT6 cells is, in part, composed of proteins characterized by acidic pIs (4.4 to 5.4), low molecular mass (M(r) 18,500-21,000), and calcium-binding; these attributes and the immunoreactivity of these proteins to anticentrin antibodies indicate that they are centrin isoforms of metazoan cells. Finally, we confirm our earlier observation that PtK2 cells contain a centrin-related protein of M(r) 165,000; QT6 cells also contain centrin-related proteins (M(r) 64,000-165,000). We conclude that centrin is a component of the pericentriolar lattice of higher eukaryotic centrosomes.

Use of p-benzoquinone for the spectrophotometric determination of certain sulphonamides

A simple spectrophotometric method for the determination of 15 sulphonamides in bulk and in dosage forms is described. The method is based on the interaction of p-benzoquinone with sulphonamides in 0.1 M hydrochloric acid. The resulting chromophore is measured at 500 nm. The effects of different variables on colour development were established. Beer's law was obeyed in a concentration range of 10-50 micrograms ml-1. Results from the analysis of different sulphonamide tablets and ophthalmic solutions marketed locally were in good agreement with that of a reference method. Correlations between A1cm(1%) and certain physical parameters such as pKa values, characteristic volume Vx, and molecular connectivity indices 1X and 1Xv were determined by linear regression equations. A poor correlation was found between A1cm(1%) and bulkiness parameters but a highly significant negative correlation was obtained with apparent pKa values.

Localization of the centrin-related 165,000-Mr protein of PtK2 cells during the cell cycle

In this study, we follow changes in localization of the centrin-related 165,000-Mr protein of PtK2 cells during the cell cycle. This protein is a component of a pericentriolar lattice that consists of pericentriolar satellites, pericentriolar matrix, and basal feet (Baron A.T., and J.L. Salisbury, J. Cell Biol. 107:2669-2678, 1988). By immunofluorescence microscopy, the 165,000-Mr protein is seen as a constellation of pericentrosomal spots. We observe that cells in late G1 and S are characterized by a dense centrosomal focus of spots with additional spots dispersed throughout the cytoplasm. In G2, one bright centrosomal focus of clustered spots is observed. As the cells proceed through prophase this single focus divides, forming two foci that move toward opposite sides of the nucleus. During prometaphase, each polar focus of spots disperses. At metaphase, the spots are distributed throughout each half-cytoplast from the poles to the chromosomes. During anaphase chromosome movement, some spots are seen beside and behind the trailing chromosome arms while others are clustered at the poles. At telophase, pericentrosomal spots radiate from the poles to surround each mass of chromatin. In early G1, pericentrosomal spots surround each newly formed nucleus. We conclude that the 165,000-Mr protein is a dynamic component of both the centrosome (pericentriolar matrix) and the mitotic apparatus (spindle matrix).