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Biomedical subjects

S F Ng

Publications and source records attributed to S F Ng.

At least 19 recordsLinked to original sources
PubMed2005

Identifying HIV/AIDS primary care development needs.

AIM: This paper reports a study aimed at identifying the primary health care experiences of people living with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) in Malaysia. The rationale behind the study was to enable informed action for developing more responsive and effective primary care. BACKGROUND: Reports such as from the World Health Organisation forecast sharp escalations in the incidence of HIV/AIDS in Malaysia and the Asia-Pacific region within the next few years. With sparse information on the course of infection on the local population and an understanding of health care needs of those afflicted, health services would be ill-prepared for projected increases. METHOD: Semi-structured interviews were conducted with a convenience sample of 99 patients attending two major HIV/AIDS clinics in Malaysia. FINDINGS: Several gaps in care provision were highlighted, such as with treatment/consultation facilities and availability and accessibility of information. What is also evident is that there are a number of good support services available but not well publicized to those in need of them. That includes health professionals who could be making appropriate referrals. The lack of communications and inter-professional working appears to be part of the problem. CONCLUSION: The findings provide baseline data and preliminary insights to government and other service providers towards advancing, optimizing and refining existing policies and infrastructure. Although the availability of a number of primary care facilities have been identified, the study indicates the need for more effective co-ordinated efforts with clear leadership to pull together scarce resources towards the aim of some degree of seamless primary care provision. It is suggested that nurses would be well placed for such a role in view of the nature of their education and training that helps prepare them for the multi-faceted role.

Adult↗
PubMed2002

Infantile isolated sulphite oxidase deficiency in a Chinese family: a rare neurodegenerative disorder.

We report the clinical, biochemical, neuroradiological, and neurophysiological findings of a 4-year-old Chinese girl with infantile isolated sulphite oxidase deficiency. This is the first reported case in our locality. She presented at the age of 5 months with refractory seizures and developmental regression, and progressed rapidly to profound psychomotor retardation, spasticity, dystonia, microcephaly, and blindness. At the age of 3.5 years, she was admitted to the intensive care unit with septic shock. Ophthalmologic examination at this time revealed bilateral dislocation of the lens. Diagnosis of this very rare disorder was made on the basis of increased levels of urinary sulphite, thiosulphate, and sulphocysteine; normal urine xanthine and hypoxanthine; normal plasma uric acid; and low plasma cystine levels. The diagnosis was confirmed by the absence of sulphite oxidase activities in skin fibroblasts. Isolated sulphite oxidase deficiency is a rare inborn error of sulphur metabolism that is difficult to diagnose on clinical features and routine metabolic tests. The presence of ectopia lentis, seizures, and progressive neurological abnormalities should alert clinicians to the diagnosis.

Amino Acid Metabolism, Inborn Errors↗
PubMed1992

Hormonal perturbations in patients with testicular cancer treated with cisplatin.

Patients with testicular cancer treated with cisplatin can undergo feminization that is understood poorly. Rat model studies recently showed that cisplatin can feminize in part the profile of hepatic steroid-metabolizing enzymes and circulating hormone levels. This study was undertaken to determine whether cisplatin similarly might contribute to the perturbations in gonadotropin or steroid hormone levels that can occur in patients undergoing cisplatin-based treatment for testicular cancer. Analysis of serum free testosterone, total testosterone, and androstenedione levels revealed that these hormones were not altered significantly in patients during a 38-week period of cisplatin-based treatment and follow-up. Estradiol levels were elevated before chemotherapy and were reduced to normal levels during treatment. This reduction was attributed to the cytotoxic effect of chemotherapy on the tumors and the resultant reduction in serum chorionic gonadotropin levels. Serum dihydrotestosterone (DHT) levels were normal before chemotherapy but progressively became elevated during treatment with cisplatin in five of ten patients examined. The rise in DHT may relate to the previously described increase in hepatic androgen 5 alpha-reductase activity in cisplatin-treated rats. Levels of the gonadotropins, luteinizing hormone, and follicle-stimulating hormone (FSH) were normal before cisplatin-based treatment was administered; however, FSH was elevated selectively during chemotherapy. This selective induction of FSH may reflect an effect of cisplatin on the hypothalamic secretion of gonadotropin-releasing hormone. Taken together, these findings suggest that cisplatin contributes to the perturbation of steroid and peptide hormone levels in patients with testicular cancer and perhaps in others undergoing cisplatin-based chemotherapy.

Adult↗
PubMed1991

N,N',N''-triethylenethiophosphoramide (thio-TEPA) oxygenation by constitutive hepatic P450 enzymes and modulation of drug metabolism and clearance in vivo by P450-inducing agents.

The cancer chemotherapeutic drug N,N',N''-triethylenephosphoramide (thio-TEPA) is oxidatively desulfurated to yield the active metabolite N,N',N''-triethylenephosphoramide (TEPA) in a reaction catalyzed by the phenobarbital-inducible rat liver P450 enzyme IIB1. In the current study, the role of constitutively expressed P450 enzymes in thio-TEPA metabolism was studied using purified P450s, isolated liver microsomes, and intact rats. Metabolism of thio-TEPA (100 microM) to TEPA by uninduced adult female and male rat liver microsomes proceeded at initial rates of 0.10 and 0.28 nmol TEPA formed/min/mg microsomal protein, respectively. Although these rates are low compared to those catalyzed by phenobarbital-induced liver microsomes (3.5 nmol TEPA/min/mg), they are sufficient to contribute to the systemic metabolism of this drug. Thio-TEPA metabolism catalyzed by uninduced female liver microsomes was approximately 70% inhibitable by antibodies selectively reactive with P450 IIC6. For the uninduced male liver microsomes, which exhibit a severalfold higher rate of thio-TEPA metabolism, enzyme activity was only 15-20% inhibitable by these antibodies but was 80-85% inhibited by an anti-P450 IIC6 monoclonal antibody cross-reactive with P450 IIC11, which is expressed only in the males. Consistent with these observations, purified P450s IIC11 and IIC6 both oxidized thio-TEPA in reconstituted systems (turnover, 1.1 and 0.3 min-1 P450-1, respectively, at 100 microM substrate), while several other constitutive hepatic P450s exhibited significantly lower or undetectable activities (turnover, less than or equal to 0.15 min-1 P450-1). Metabolism of thio-TEPA by purified P450 IIC11 was associated with a time-dependent inactivation of the cytochrome analogous to that previously shown to accompany thio-TEPA metabolism catalyzed by P450 IIB1. Depletion of hepatic P450 IIC11 by cisplatin treatment of adult male rats led to a 70% reduction of TEPA formation catalyzed by the isolated liver microsomes, suggesting that cisplatin may influence thio-TEPA pharmacokinetics when these two drugs are given in combination. The extent to which hepatic P450s contribute to thio-TEPA metabolism and clearance in vivo was assessed by monitoring thio-TEPA and TEPA pharmacokinetics in rats that exhibit widely differing rates of microsomal thio-TEPA metabolism, i.e., uninduced female and male rats, and male rats treated with the P450 IIB1 inducers clofibrate and phenobarbital. In accord with the microsomal activities, conversion of thio-TEPA to TEPA was less extensive and thio-TEPA elimination slower in female than in male rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Cosubstrate binding site of Pseudomonas sp. AK1 gamma-butyrobetaine hydroxylase. Interactions with structural analogs of alpha-ketoglutarate.

Forty-one aromatic and aliphatic analogs of alpha-ketoglutarate were studied kinetically for their interaction with the alpha-ketoglutarate binding site of gamma-butyrobetaine hydroxylase obtained from Pseudomonas sp. AK1. Together, the compounds represent structural permutations probing the contribution of: 1) the C5 carboxyl group of alpha-ketoglutarate (domain I); 2) the C1-C2 keto acid moiety of alpha-ketoglutarate (domain II); 3) the distance between domains I and II; and 4) the spatial relationship of the two domains required for optimal interaction with the cosubstrate binding site. All compounds were competitive inhibitors for alpha-ketoglutarate (Km 0.018 mM). Functionally, two subsites of the cosubstrate binding site were evident: subsite I for polar interaction with the C5 carboxyl group, and subsite II, comprising of two distinct cis-oriented coordination sites of the catalytic ferrous ion which interact with the C1-C2 keto acid moiety. The most efficient inhibitors were pyridine 2,4-dicarboxylate (Ki 0.0002 mM) and 3,4-dihydroxybenzoate (Ki 0.0006 mM). Both compounds contain a carboxyl group and a chelating moiety corresponding to domains I and II of alpha-ketoglutarate, respectively. The fixed orientation of these groups in both analogs was used to assess intersubsite distance and spatial relationship required for optimal interaction with the cosubstrate binding site. Binding at subsite I and chelation at subsite II were indispensible for effective competitive inhibition. The distance between these two domains also helped determine whether attachment at the cosubstrate binding site would be catalytically productive. This was emphasized by the failure of either oxaloacetate or alpha-ketoadipinate to promote hydroxylation. Optimal interdomain distance, however, was not sufficient for cosubstrate utilization, as pyridine 2,4-dicarboxylate, with an interdomain distance identical to alpha-ketoglutarate in its staggered conformation, did not sustain hydroxylation. In the overall, these studies suggest that alpha-ketoglutarate utilization occurs in a ligand reaction at the active site ferrous ion of gamma-butyrobetaine hydroxylase. This is of particular interest since the delineated stereochemical mode of oxidative decarboxylation could generate the reactive oxo-iron species that was shown experimentally to promote gamma-butyrobetaine hydroxylation by an abstraction-recombination mechanism (Blanchard, J. S., and Englard, S. (1983) Biochemistry 22, 5922-5928; Englard, S., Blanchard, J. S., and Midelfort, C. F. (1985) Biochemistry 24, 1110-1116).

Binding Sites↗
PubMed1991

Xenobiotic induction of P-450 PB-4 (IIB1) and P-450c (IA1) and associated monooxygenase activities in primary cultures of adult rat hepatocytes.

1. The long-term maintenance of metabolism of representative drugs and steroid hormone substrates by cytochromes P-450, and their inducibility, was investigated in primary cultures of adult rat hepatocytes. Collagenase-isolated cells were seeded on collagen-coated tissue culture dishes and cultured in Chee's essential media in the presence or absence of phenobarbital (PB, 0.75 mM, 96 h or continuously) and 3-methylcholanthrene (MC, 5 microM, 48 h) for up to 45 days. 2. Hepatic P-450-dependent metabolism of diazepam to its primary oxidized metabolite was inducible by PB both in vivo (monitored in isolated liver microsomes) and in cultured cells (up to 100% and 400% increases in the formation of temazepam and nordiazepam, respectively, after 25 days in culture). Hepatocyte microsomal androstenedione 16 beta-hydroxylase activity was also induced by PB treatment of the hepatocytes (350-650% increase in 20-day-old cells). 3. Western blot analysis revealed that immunoreactive P-450 form PB-4 (IIB1), which catalysed the N-demethylation of diazepam to yield nordiazepam as well as androstenedione 16 beta-hydroxylation when assayed in a purified enzyme system, was substantially elevated following PB treatment of the cultured cells. Similarly, MC induced 7-ethoxycoumarin O-deethylase activity (up to 2000% increase from 5 to 45 days) as well as immunoreactive P-450c (IA1) in the hepatocyte cultures. 4. These studies demonstrate that cytochrome P-450 activities can be maintained, and also induced, after extended periods of time in hepatocytes cultured using a simple collagen mixture as substrate and a commercially available tissue culture media. This culture system should provide an important tool for further studies of P-450-dependent xenobiotic metabolism in a well-defined, liver-derived cellular system.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1990

Biotransformation of N,N',N''-triethylenethiophosphoramide: oxidative desulfuration to yield N,N',N''-triethylenephosphoramide associated with suicide inactivation of a phenobarbital-inducible hepatic P-450 monooxygenase.

Oxidative metabolism of the polyfunctional alkylating agent N,N',N''-triethylenethiophosphoramide (thio-TEPA) was studied in isolated rat liver microsomes and purified, reconstituted cytochrome P-450 (P-450) enzyme systems in order to elucidate the pathways of drug oxidation and to identify the possible contributions of individual P-450 enzymes to the bioactivation of this chemotherapeutic agent. Rat liver microsomes were found to catalyze conversion of thio-TEPA to its oxo metabolite, N,N',N''-triethylenephosphoramide (TEPA), in a P-450-dependent reaction that was markedly stimulated by prior in vivo treatment with drug inducers of hepatic P-450 subfamily IIB (phenobarbital), but not by pretreatment with inducers of P-450 subfamilies IA (beta-naphthoflavone) or IIE (isoniazid). Thio-TEPA depletion and TEPA formation catalyzed by phenobarbital-induced liver microsomes were both inhibited by greater than 90% by antibodies selectively reactive with P-450 PB-4 (gene product IIB1), the major phenobarbital-inducible rat liver microsomal P-450 form, but not by antibodies inhibitory toward 7 other rat hepatic P-450s. Oxidation of thio-TEPA to TEPA was also catalyzed by purified P-450 PB-4 (Km (app) 19 microM; Vmax (app) = 11 mol thio-TEPA metabolized/min/mol P-450 PB-4) following reconstitution of the cytochrome with NADPH P-450 reductase in a lipid environment. Metabolism of thio-TEPA by P-450 PB-4 was associated with a suicide inactivation of the cytochrome characterized by kinactivation = 0.096 min-1, KI = 24 microM, and a partition ratio of 136 +/- 28 (SD) mol thio-TEPA metabolized/mol P-450 inactivated. The thio-TEPA metabolite TEPA, however, did not inactivate the cytochrome, nor was it subject to further detectable metabolism. In microsomal incubations, metabolism of thio-TEPA led to the inactivation of P-450 PB-4 (steroid 16 beta-hydroxylase) as well as P-450 IIIA-related enzymes (steroid 6 beta-hydroxylase) and the P-450-independent enzyme steroid 17 beta-hydroxysteroid:NADP+ 17-oxidoreductase, as demonstrated by use of the P-450 form-selective steroidal substrate androst-4-ene-3,17-dione. In contrast, little or no inactivation of microsomal P-450 IIA-related enzymes (steroid 7 alpha-hydroxylase) or microsomal NADPH P-450 reductase was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Effect of biosynthetic human growth hormone on insulin action in individual tissues of the rat in vivo.

Excessive endogenous production or exogenous administration of human growth hormone (hGH) causes insulin resistance at both the hepatic and extrahepatic levels. However, which extrahepatic tissues are involved have not been defined. We have examined the diabetogenic action of authentic biosynthetic hGH on whole body glucose disposal, hepatic glucose output, and glucose metabolism in individual peripheral tissues. The use of a highly purified preparation of the hormone allowed us to examine the isolated effects of 22K hGH. The euglycemic hyperinsulinemic (approximately 100 mU/L) clamp plus 3H-2-deoxyglucose technique was used to quantitate the effects of hGH on insulin action in vivo. Administration of biosynthetic hGH at a dose of 10 IU/kg/24 h for 48 hours in male Wistar rats (approximately 340 g) produced a highly significant decrease in the steady state clamp glucose infusion rate (GIR) when compared with controls (8.1 +/- 0.6 v 18.7 +/- 0.7 mg/kg/min, P less than .001), reduced insulin-mediated suppression of hepatic glucose output (Ra) (3.9 +/- 0.6 v 0.7 +/- 0.3 mg/kg/min, P less than .05) and a decreased clamp glucose disposal rate (Rd) (12.0 +/- 0.4 v 18.10 +/- 1.1 mg/kg/min, P less than .001). There was a significant decrease in insulin-mediated glucose uptake as indicated by tissue accumulation of [3H]-2-deoxyglucose phosphorylation in diaphragm and hindlimb muscles. Insulin action was more substantially reduced in muscles (approximately 50%) than in adipose tissues (approximately 20%). These studies confirm that the diabetogenic action of hGH in the rat is due to a combination of inhibition of insulin suppression of hepatic glucose output and inhibition of the uptake and subsequent utilization of glucose in skeletal muscles.

Adipose Tissue↗
PubMed1989

Control of development of the oral apparatus of Paramecium during sexual reproduction: an embryological perspective.

This study shows that development of the new soma during sexual reproduction in ciliates can be conceptualized on the same basis as embryogenesis in multicellular organisms. In conjugating Paramecium, development of a new oral apparatus takes place during fertilization and the first three divisions of the zygotic nucleus and completes well before the postsexual cell undergoes the first cell fission. The control of oral development is analyzed by microsurgical removal of the zygotic nucleus or the postzygotic nuclei from conjugants. The enucleated exconjugants can pass through an early hurdle in oral development (the initiation of oral membranelle assembly) and subsequently develop an oral apparatus. Such oral apparatuses nevertheless exhibit structural and functional abnormalities including fragmentation and misalignment of oral membranelles, absence of the postoral microtubular bundle, reduction in the length of buccal cavity, and impaired phagocytosis. Other stomatogenic aspects, such as the arrangement of basal bodies in the oral membranelles, remain unaffected. The two groups of exconjugants, one derived from cells enucleated at the zygotic stage, and the other at the postzygotic stage, exhibit the same types of oral abnormality. We conclude that (i) the zygotic nucleus is not essential for the initiation of oral membranelle assembly. The existence of zygotic signals for subsequent oral development is not ruled out, but these are insufficient. (ii) Postzygotic nuclei, as well as maternal nuclei (the old somatic nucleus and meiotic derivatives of the germ nucleus), control oral development. This reveals a parallelism between postsexual development in ciliates and the early embryology of multicellular organisms, in their reliance on information provided by maternal, as well as early postzygotic nuclei. (iii) The activity of the old somatic nucleus alone is not sufficient for the later stages of oral development. Probably, some stomatogenic functions of the old somatic nucleus normally utilized for the later stages of oral development in binary fission are inactivated during sexual reproduction. Alternatively, the old somatic nucleus may rely on some critical conditions prescribed by the postzygotic nuclei in order to act.

Animals↗
PubMed1989

5-Azacytidine affects the programming of expression of the somatic nucleus of Paramecium.

This report introduces a new system in the study of programming of genomic function during development of the somatic nucleus of Paramecium tetraurelia. Previous works have established a definite, but replaceable, role of the germ nuclei (micronuclei) in oral development in the asexual cycle; their removal from the cell generates viable amicronucleate cell lines, which characteristically suffer a transient period of growth depression marked by abnormal oral development. Such cell lines gradually recover, showing that a compensatory mechanism is activated in the absence of the germ nuclei to bring the cell back to near-normal. To test the notion that the somatic nucleus (macronucleus) is involved in this compensation, cells possessing micronuclei were treated with 5-azacytidine during sexual reproduction when new somatic nuclei develop. These cells were then propagated asexually for a number of fissions in the absence of the drug, and thereafter micronuclei were removed from them. The amicronucleate cell lines generated in this manner clearly did not suffer a depression as severe as the untreated controls did in terms of growth rate and oral development, and they recovered much sooner. This supports the notion that the somatic nucleus is the physical basis of the compensatory mechanism. This study suggests that the stomatogenic sequences in question normally become repressed in the somatic nucleus developing in sexual reproduction, and that 5-azacytidine administered to the cells at this time could alter this programme which then persists during subsequent asexual propagation. The possibility that the somatic nucleus is programmed by methylation of cytosine at the 5' position is discussed.

Animals↗
PubMed1986

The role of the micronucleus in stomatogenesis in sexual reproduction of Paramecium tetraurelia: laser microbeam irradiation of the micronucleus.

Fifteen amicronucleate cell lines and 22 cell lines with defective micronuclei were obtained following selective laser microbeam irradiation of the micronucleus. The amicronucleate cell lines showed reduced growth rate and formed abnormal oral apparatuses in asexual reproduction, and failed to produce any oral apparatus in autogamy, in agreement with previous observations on amicronucleate cells obtained by micropipetting. The 22 cell lines with defective micronucleus exhibited various abnormalities of the oral apparatus newly formed during autogamy. These abnormalities included the arrest of membranelle assembly, reduction in the length of the buccal cavity and oral membranelles, disruption of the organization of the membranelles, quadrulation of the dorsal peniculus, and failure of addition of membranellar basal body rows. Hence the micronucleus plays multiple roles in sexual stomatogenesis, deciding early steps of oral membranelle assembly and affecting their subsequent patterning. Our results agree with the notion that the micronucleus acts during a critical period between the second meiotic division and up to the formation of the zygotic nucleus to control the early stage of oral membranelle assembly. Laser microbeam irradiation might have created recessive mutations and/or chromosomal aberrations, which were expressed during this critical period with the formation of abnormal postmeiotic nuclei.

Animals↗
PubMed1985

Changes in ornithine decarboxylase activity and polyamine levels during the growth of Tetrahymena thermophila cultures.

Ornithine decarboxylase activity and polyamine levels were determined at various growth phases of Tetrahymena thermophila cultures. Enzyme activity and intracellular polyamines increased in exponentially growing cells and peaked just before the stationary phase. Putrescine was the predominant polyamine and spermidine and spermine concentrations were low throughout. The increase in putrescine level can be totally accounted for by the enzyme activity detected, provided that there is an ample supply of the precursor, L-ornithine.

Animals↗
PubMed1984

Putrescine biosynthesis in Tetrahymena thermophila.

The putrescine-biosynthesis pathway in Tetrahymena thermophila was delineated by studying crude extracts prepared from exponentially growing cultures. A pyridoxal phosphate-stimulated ornithine decarboxylase activity competitively inhibited by putrescine was detected. CO2 was also liberated from L-arginine, but analyses by t.l.c. and enzyme studies suggested that the activity was not due to arginine decarboxylase, nor could enzyme activities converting agmatine into putrescine be detected. We conclude that the decarboxylation of L-ornithine is probably the only major route for putrescine biosynthesis in this organism during exponential growth.

Agmatine↗
PubMed1983

Nuclear differentiation in Paramecium tetraurelia. Transplantation of vegetative micronuclei into early exconjugants.

The micronucleus of Paramecium tetraurelia normally gives rise to the macronucleus by going through the series of nuclear events of meiosis, mitosis and fusion during sexual reproduction. By transplanting the micronucleus from vegetative cells into early exconjugants, we have persuaded the micronucleus to take a short cut to differentiate directly into a macronucleus. This demonstrates that the course of development of the micronucleus is flexible and can be altered by stage-specific cytoplasmic factors.

Animals↗
PubMed1979

Unidirectional regeneration is an intrinsic property of longitudinal microtubules in Tetrahymena--an in vivo study.

The cortex of Tetrahymena contains a regular array of longitudinal microtubular bands (lms) next to basal body rows running from pole to pole. The lm exhibits a predominant unidirectionality in assembly. The direction of regeneration following breakage of the microtubules is from posterior to anterior of the cell. When the lm and the accompanying basal body row are rotated 180 degrees (inverted), so that their polarity is opposite to that of the cell, the predominant direction of regeneration exhibited by the inverted lm is from anterior to posterior. This shows that the lm has an inherent direction of regeneration independent of cellular polarity. This implies that the microtubules constituting the lm have an intrinsic property which controls the direction of assembly. This finding is in accord with the in vitro demonstration using Chlamydomonas flagellar fragments. On the basis of this finding and also the possible pattern of arrangement of the microtubules constituting the lm, it is suggested that growth of the lm involves both elongation of pre-existing microtubules constituting the lm and also laying down of new ones.

Animals↗
PubMed1978

Directionality of microtubule assembly: an in vivo study with the ciliate Tetrahymena.

A temperature-sensitive mutant homozygous for the recessive gene molb in Tetrahymena thermophila offers opportunity for studying the direction of microtubule assembly in vivo. At 39 degrees C the mutant fails to divide properly; the 2 daughter animals remain attached and bend over each other. As revealed by protargol staining, the bending results in acute turning and breaking of some of the longitudinal microtubular bands close and parallel to the surface. Hence, 2 broken microtubular ends are available for study of the problem of directionality of microtubule assembly, by assessing which of the 2 ends regenerates. In most cases the posterior portion of the longitudinal microtubular band regenerates. The present study hence supports the conclusion based on in vitro observation in other systems that microtubule assembly is predominantly unidirectional.

Animals↗
PubMed1977

180 degrees rotation of ciliary rows and its morphogenetic implications in Tetrahymena pyriformis.

With quasi-surgical techniques, longitudinal somatic ciliary rows in Tetrahymena pyriformis have been rotated 180 degrees. New structures formed in the rotated ciliary rows during growth and reproduction are disposed 180 degrees opposite to their normal positions or orientations, confirming the earlier findings of Beisson and Sonneborn on Paramecium. However, during cell fission the rotated ciliary rows exhibit abnormality in orientation along the fission zone; the configuration of these rows near the anterior end of the posterior product of fission is consequently affected. Rotated ciliary rows have been employed as a tool in the analysis of morphogenetic problems: (a) The contractile vacuole pore is normally located on the left side of a ciliary row; but it is on the right of inverted rows. Hence, the morphogenetic properties of the two sides of the ciliary row associated with the contractile vacuole pore are different and this difference is the sole determinative factor as to the side of the ciliary row on which the contractile vacuole pore is located. (b) The process that generates the rotated ciliary rows frequently also brings about the implantation of an extra band of longitudinal microtubules at a specific site on the cell surface. This extra structure is inheritable, which opens up opportunities for the study of microtubular assembly in vivo.

Cell Division↗