Differences in school factors associated with adolescent HPV vaccination initiation and completion coverage in three Australian states

BACKGROUND

Schools are the primary setting for the delivery of adolescent HPV vaccination in Australia. Although this strategy has achieved generally high vaccination coverage, gaps persist for reasons that are mostly unknown. This study sought to identify school-level correlates of low vaccination course initiation and completion in New South Wales, Tasmania, and Western Australia to inform initiatives to increase uptake.

METHODS

Initiation was defined as the number of first doses given in a school in 2016 divided by vaccine-eligible student enrolments. Completion was the number of third doses given in a school in 2015-2016 divided by the number of first doses. Low initiation and completion were defined as coverage ≤ 25thpercentile of all reporting schools. We investigated correlations between covariates using Spearman's rank correlation coefficients. Due to multicollinearity, we used univariable logistic regression to investigate associations between school characteristics and low coverage.

RESULTS

Median initiation was 84.7% (IQR: 75.0%-90.4%) across 1,286 schools and median completion was 93.8% (IQR: 86.0%-97.3%) across 1,295 schools. There were strong correlations between a number of school characteristics, particularly higher Indigenous student enrolments and lower attendance, increasing remoteness, higher postcode socioeconomic disadvantage, and smaller school size. Characteristics most strongly associated with low initiation in univariate analyses were small school size, location in Tasmania, and schools catering for special educational needs. Low completion was most strongly associated with schools in Tasmania and Western Australia, remote location, small size, high proportion of Indigenous student enrolments, and low attendance rates.

CONCLUSION

This study provides indicative evidence that characteristics of schools and school populations are associated with the likelihood of low initiation and completion of the HPV vaccination course. The findings will guide further research and help target initiatives to improve vaccination uptake in schools with profiles associated with lower coverage.

The counting and sizing of spermatozoa from ten animal species using a Coulter counter

Accurately calibrated Coulter Counters, Models ZB Industrial and F, were used to count and size spermatozoa before and after Zaponin treatment which lyses accompanying debris, droplets and peripheral sperm cytoplasm. Sperm specimens from the cauda epididymis of the rabbit, Guinea pig, hamster, rat and mouse were without accompanying particles and could be sized without Zaponin treatment. The large acrosome cap of the guinea pig swelled rapidly when the spermatozoa were released into an isotonic solution and measurement was only possible after equilibrium had been reached. Zaponin treatment completely dissolved rat and hamster spermatozoa within a few seconds and about 50% of the mouse spermatozoa. Spermatozoa form the cauda epididymis of the bull were accompanied by some unspecific debris which made size determination without Zaponin treatment difficult. A separate population of cytoplasmic droplets was not present and the amount of accompanying cytoplasm, as shown by its removal with Zaponin, was the least for the species examined. The size of spermatozoa in ejaculated specimens from the dog varied considerably according to whether the cytoplasmis droplet was still present, but after Zaponin treatment all specimens were about the same size. Ejaculated specimens from the European wild boar contained a separate population of small droplets which were sufficiently different in size from the spermatozoa to allow separate counting and sizing without Zaponin treatment. Ejaculated specimens from the Rhesus monkey required incubation to release the spermatozoa from the clot before they could be counted and sized. Their size tended to vary slightly according to the length of incubation. Ejaculated specimens from the rabbit and from man were so heavily contaminated with debris that counting and sizing was not possible without Zaponin treatment. The relationship between the amount of debris and the numbers of spermatozoa was extremely variable. The debris in human specimens was separated from the spermatozoa by downward fractionation of the motile spermatozoa into increasing concentrations of bovine serum albumin, so allowing measurement of untreated spermatozoa for the first time. The sperm size distribution curves for all the ten species examined, both before and after Zaponin treatment, were positively skewed. The peaks were broader and flatter when Zaponin was not used. Sperm sizes, in terms of total volume and of the diameter of a sphere of that volume, are given for all the species at both the mode and the mean of the size distribution curves. After Zaponin treatment the mean size was between a volume of 15 and 50 mum3 or an equivalent spherical diameter of 3-5 mum. Before Zaponin treatment all the sperm types were greater than 20% larger by volume and the mean volume was between 25 and 190 mum3.

Parathyroid hormone: another pregnancy protein present in human seminal plasma and amniotic fluid

Parathyroid hormone (PTH) has been found in human seminal plasma at concentrations of 302 +/- 65 (222-482) pmol l-1 (n = 16), which is about 5 times the concentration in human blood serum. Concentrations in human amniotic fluid at 16-22 weeks of gestation were 43 +/- 9 (28-65) pmol l-1 (n = 24), which is about 80% of the concentration in blood serum. The Amersham assay uses an antiserum raised against the synthetic middle piece of the PTH molecule from the parathyroid glands. It estimates amino acids 44-68 of the 84 amino acid intact molecule, together with fragments containing this part of the chain. It is considered that a placental type of parathyroid hormone was being measured, some of which escapes into the amniotic fluid. The placenta contains a complete PTH-dihydroxyvitamin D3 system that causes the absorption of more calcium from the gut for foetal needs during pregnancy. It is postulated that the seminal vesicles also contain a PTH-dihydroxyvitamin D3 system that has a paracrine action in passing large amounts of calcium into the ejaculate.

Ferritin: another pregnancy-specific protein in human seminal plasma and amniotic fluid, as estimated by six methods

Large quantities of ferritin were found in both seminal plasma and amniotic fluid, but there was a wide spread of results for each of six new non-radioactive monoclonal assays designed to give the same results for ferritin in blood serum. Correlation of values between the various assays was also poor, but after the exclusion of outliers it was possible to calculate approximate ratios for the concentrations. For seminal plasma, the Amersham 'Amerlite' luminescence immunoassay gave the lowest concentrations at 81 +/- 56 ng ml-1 WHO 80/602 (mean +/- SD, n = 43). Relative to this value as 100%, the other assays gave:Flow 'Monoscan' colorimetric IEMA = 161%; Pharmacia-LKB 'DELFIA' fluoroimmunoassay = 174%, Walker 'Synelisa' colorimetric ELISA = 182%; Abbott 'IMx' MEIA = 207%, while the results from the Ramco colorimetric ELISA were much higher and not parallel to the other assays. For amniotic fluid, the Amersham 'Amerlite' LIA gave 127 +/- 95 ng ml-1 (n = 38), taken as 100%, and the ratios for the other assays were:Abbott also approximately 100% but with a wide spread; Walker 43%, Pharmacia-LKB 22% and Ramco 148%. The Flow assay produced 15 zero values from 38 samples, and values were also very low in another 17 samples, so that no comparison with the other assays was possible. An attempt was made to determine the proportion of the different types of isoferritins being estimated. The Pharmacia-LKB assay estimated 90% of the theoretical concentration for pure liver ferritin, 42% of that from the placenta, 26% of that from the heart and 13% of that from the spleen. The other assays gave different proportions.

Serum cortisol in adrenal hirsutism as estimated by five different methods

Serum cortisol had been estimated in 152 hirsute women complaining of fertility problems, of whom 36 were subsequently diagnosed as having adrenal hirsutism and 10 as having congenital adrenal hyperplasia (steroid 21-hydroxylase deficiency), using five methods: an in-house tritium radioimmunoassay after extraction with ethanol; the Diagnostic Products Corp. "Coat-a-count" iodinated direct radioimmunoassay; the Pharmacia-LKB "DELFIA" lanthanum-enhanced fluoroimmunoassay; the Amersham "Amerlite" luminescence immunoassay; and the Walker "Synelisa" enzyme-linked immunoassay. Although stripped pool serum samples containing weighed amounts of cortisol produced acceptable values in all assays, the patient samples showed a number of high results, much greater than the accepted normal upper limit of 250 ng/ml (25 micrograms/dl, 690 nmol/l). This was especially so in 21-hydroxylase deficiency, when cortisol values should be very low. Only the luminescence and iodinated assays produced very low values after dexamethasone suppression. After the outliers had been excluded, only the iodinated assay showed a good statistical agreement with the more elaborate tritium assay. The most specific assay was the luminescence method, which produced generally lower results in most cases. This was selected as the new routine method. The unreliable cortisol results in adrenal hirsutism are attributed to high cross-reaction of the antiserum in each of the assays with 17-hydroxyprogesterone, progesterone and 21-deoxyderivatives of cortisol and deoxycorticosterone. In general, all standard and commercially available cortisol assays appears to be unsuitable for cortisol estimation in 21-hydroxylase deficiency, and probably also for neonates.

Vasopressin: another pregnancy protein in human seminal plasma

Human vasopressin (arginine-vasopressin, AVP, antidiuretic hormone, ADH) was estimated, after protein precipitation and extraction in ethanol, using a new radioimmunoassay from Immuno Technology Service, Wijchen, Netherlands. Concentrations in human seminal plasma were 1.84 +/- 1.23 (0.6-4.1) pg/ml, estimated in good duplicates in all 20 samples, where 1 pg = 0.410 uIU/ml WHO 1st 77/501. This is about the same concentration as in blood serum, for which levels up to 8 pg/ml are found by the same kit. In contrast, only trace amounts of vasopressin were found in amniotic fluid at 16-22 weeks of gestation, with zero values in 8 of 19 samples, while another 9 samples showed zero in one duplicate and up to 0.46 pg/ml in the other duplicate, and one sample showed 0.09 pg/ml in good duplicates.

Suppression of maternal pituitary thyroid-stimulating hormone during pregnancy

Maternal serum thyroid-stimulating hormone (TSH) has been estimated in 38 pregnant women with three new specific nonradioactive monoclonal immunoassays which can measure very low concentrations. Values for the Pharmacia-LKB 'DELFIA' fluoroimmunoassay and for the Amersham 'Amerlite' luminescence immunoassay were statistically identical over the range 0.15-1.5 uIU/ml WHO 2nd IRP 80/558, but thereafter the Amersham values were slightly lower. The Abbott 'IMx' assay system gave slightly higher results commensurate with the quoted higher non-pregnant normal values. The Amersham assay was preferred on practical grounds. There was no relationship of TSH levels to HCG levels, or to the length of pregnancy. Four women had apparently zero TSH levels by the Amersham and Pharmacia-LKB assays, although the Abbott assay could detect very low concentrations. Together with women whose TSH levels were below the normal non-pregnant range for each assay, there were a total of eight women (21%) with TSH levels below 'normal'. This suppression of maternal pituitary TSH levels during pregnancy was considered to be due to the central feedback inhibitory thyrotrophic activity of HCG, as a separate placental thyrotrophic hormone is believed not to exist. The enlargement of the maternal thyroid gland and the increased production of thyroid hormones during normal pregnancy is likewise to be attributed to HCG rather than to an increase in TSH production.

Cortisol and transcortin in human seminal plasma and amniotic fluid as estimated by modern specific assays

Cortisol concentrations in human seminal plasma, as estimated by the very specific Amersham 'Amerlite' luminescence immunoassay, were 176 +/- 43 (85-260) nmol/l, that is, 63.7 +/- 15.5 (31-94) ng/ml (mean +/- SD, n = 21). This is about 60% of random levels in blood serum and is the first description of cortisol in seminal fluid. In human amniotic fluid at 16-22 weeks of gestation, cortisol concentrations were lower, at 72.6 +/- 14.6 (63-124) nmol/l, that is, 29.3 +/- 5.3 (23-45) ng/ml (n = 21). Concentrations were about 15% of random maternal serum levels in the second trimester of pregnancy. The cortisol concentrations in both fluids were considerably higher than those reported for saliva, which has a mean of about 10 nmol/l. Transcortin (corticosteroid binding globulin, CBG), has been found in human seminal plasma and amniotic fluid for the first time. Concentrations were low, with values up to 12 micrograms/ml, with no significant difference between the two fluids, when using the IRE-Megenix monoclonal iodinated radioimmunoassay. Transcortin concentrations were about 10% of levels in non-pregnant blood serum, compared with about 0.1% for saliva. The higher concentrations of transcortin could perhaps account for the greater diffusion of cortisol into seminal plasma and amniotic fluid. The presence of beta-endorphin, ACTH and cortisol in amniotic fluid, seminal fluid, ovarian follicular fluid, endometrial fluid and gastric fluid may possibly, indicate the existence of a small paracrine ACTH-cortisol axis in the relevant secretory tissues.

Cryopreservation of human semen

A review is given of the techniques for the cryopreservation of human semen, including the preparation of cryoprotective media, the use of ampoules, straws, and pellets, and freezing and thawing techniques. The use of cryopreserved semen for therapeutic artificial insemination by donor is described. The advantages of cryopreserved semen over fresh donor semen mostly lie in the ability to exclude infections before use and the extra convenience, in spite of the lower success rate and increased cost. The recovery of sperm motility on thawing is described, as are other methods for assessing the degree of damage to the spermatozoa by the freezing procedure. The success rates reported by large semen banks are summarized.

Growth hormone levels in maternal serum during pregnancy

Maternal growth hormone (GH) levels during pregnancy have been variously reported to be suppressed or, more lately, to be increased. In an attempt to clarify this point, maternal GH levels were estimated with two modern GH polyclonal radio-immunoassays (RIAs) and a new monoclonal enzyme-linked immunoassay (ELISA). The Cambridge Medical Diagnostics RIA and the more specific bioMérieux RIA gave similar results in control non-pregnant patients with raised GH levels, while the monoclonal ELISA gave slightly lower values. The bioMérieux assay gave results about 10 times higher than the Cambridge assay during pregnancy, at 12-61 ng/ml at 16-20 weeks and 47-153 ng/ml at 28-39 weeks (total n = 27). These high 'GH' levels did not correlate with maternal levels of prolactin or human placental lactogen. It is presumed that some unknown GH-like molecule(s) are being estimated in this assay, possibly the recently discovered human chorionic GH. That this is not pituitary GH was confirmed by the monoclonal ELISA, by which GH levels were almost undetectable during pregnancy.

Estimation of serum sex hormone-binding globulin by five direct and two indirect methods

Serum sex hormone-binding globulin (SHBG) has been estimated over the range 2-190 nM by six commercially available methods. The Farmos immunoradiometric assay (IRMA) and the Pharmacia-LKB DELFIA fluoroimmunoassay, which use the same monoclonal antiserum, produced statistically identical but widely spread results. The Techland polyclonal radioimmunoassay produced similar results but was considerably less sensitive, and agreement with the other two direct methods was poor at low concentrations. These three direct methods gave slightly higher results than those obtained with the two indirect methods: the BioMerieux concanavalin-A-binding method and, especially, the Serono ammonium sulphate precipitation method. The Diagnostic Products monoclonal IRMA gave results that were up to double the values obtained with the other five methods and is considered unsatisfactory. Monoclonal antibodies are now available for the direct estimation of SHBG, although an amino acid sequence has not yet been published for this protein, and there is still some controversy about the size of its structural units.

Artificial insemination with fresh donor semen

A review is given of the use of fresh donor semen for therapeutic artificial insemination. This includes a section on the legal, ethical, and psychological aspects as seen from the point of view of various cultures. Topics covered are the indications for donor insemination, the selection of donors, and the techniques in common use. The success rate is described together with the sex ratio of the neonates. Short mention is made of short-term office semen preservation and the obsolete technique of mixed husband-donor insemination.

Comparison of human chorionic gonadotrophin in human urine and amniotic fluid as estimated by a polyclonal and by a specific monoclonal assay in very early pregnancy

Urinary human chorionic gonadotrophin (HCG) was estimated in 42 samples from patients in very early pregnancy or shortly after early spontaneous abortion, in which initial testing showed a positive urinary HCG in the Hybritech Tandem ICON II monoclonal 2 min test. There were no false positives with this test even when the blue colour was difficult to distinguish from the white background, i.e. considerably less than the calibration blue spot at 50 mIU/ml. The Serono polyclonal beta-HCG radioimmunoassay (RIA) detected urinary intact HCG (plus free beta-subunit) at concentrations as low as 10 mIU/ml IS 61/6 for bioassay (the old standard), i.e. approximately 22 mIU/ml 1st IRP 75/537 for immunoassay (the new standard). The LKB-Pharmacia DELFIA monoclonal fluoroimmunoassay (FIA) detected urinary intact HCG, without free beta-subunit, to a minimum concentration of 18 mIU/ml 75/537. The proportion of monoclonal/polyclonal was 2-155%. In normal amniotic fluid at 16-20 weeks of pregnancy, HCG concentrations were 3180 +/- 2270 (755-11,000) mIU/ml with the FIA.

Human chorionic gonadotrophin in human seminal plasma as shown with assays using monoclonal antibodies

Human chorionic gonadotrophin (hCG) has been estimated in 79 samples of human seminal plasma using three different methods. The Serono "ter" double antibody-polyethylene glycol "hCG-beta" radioimmunoassay, which uses a polyclonal antibody and estimates intact HCG plus free beta-subunit, gave concentrations of 37 +/- 21 (18-112) mIU/ml 1st IRP 75/537 (n = 46). Concentrations were much less with assays that utilised monoclonal antisera. The Pharmacia-LKB "DELFIA" fluoroimmunoassay, which estimates intact hCG only, failed to detect hCG in 16/76 (21%) of samples and detected only a trace (less than 2 mIU/ml) in 32 samples, but was able to estimate authentic hCG in 28 samples, the highest concentration being 25 mIU/ml. The proportion monoclonal/polyclonal hCG in these samples was highly variable at 4-122 (mean 37) %. The. Medgenix oligo-monoclonal immunoradiometric assay, which estimates intact hCG plus free beta-subunit more specifically, gave even lower concentrations. It failed to detect hCG in 6/54 (11%) of samples and detected only a trace in 27 samples, but was able to estimate hCG in 21 samples, the highest concentration being 20 mIU/ml. The proportion of monoclonal/polyclonal hCG in no case exceeded 0.2%. It is concluded that authentic hCG does occur in human seminal plasma, but only in about a third of samples. The origin of this hCG is discussed.

Selenium, rubidium and zinc in human semen and semen fractions

The levels of selenium, rubidium and zinc were determined in samples of semen, seminal plasma and spermatozoa from men with suspected infertility, together with several parameters of semen quality. The proportion of whole semen selenium present in sperm increased with increasing sperm count from 0 to 40%. For rubidium 98 +/- 4% and for zinc 95 +/- 8% of the total amount in semen was contained in seminal plasma. In seminal plasma a positive correlation was found between the levels of zinc and selenium, and between the levels of zinc and rubidium, indicating that, like zinc, selenium and rubidium in seminal plasma also derive mainly from the prostate gland. Semen quality parameters, such as sperm motility, vitality, speed and morphology, were not correlated with the contents of the three elements in either whole semen or seminal plasma. As the seminal content of selenium is dependent on the proportion of prostatic secretion in seminal plasma and on the sperm count, and both factors can vary considerably, the selenium level of whole semen does not appear to be a suitable parameter for investigation of the relationship between selenium and semen quality. Provisional measurements suggest lower sperm selenium levels at abnormally low or high sperm counts.

Determination of human sperm count and sperm motility using a laser beam and the Doppler effect (LAZYMOT machine)

For 25 consecutive human semen samples, a comparison was made of sperm count and sperm motility values obtained by routine manual methods and by using a machine that measures these functions by analysing the deflection of an impinging laser beam (Lazymot machine). Sperm counts in undiluted semen were approximately 5 times higher with the laser machine. As sperm counts increased to about 300 million/ml the counts obtained by the two methods converged as the chance of the beam hitting a spermatozoon and not another type of particle increased. In semen diluted 1 + 4 with Baker's solution, the uncorrected laser count agreed well with the sperm count obtained using a haemocytometer. Multiplication of the laser count by 5 did not reach the same count as that measured in the undiluted sample, showing that the dilution had dissolved some of the smaller particles. It was recommended to measure laser percentage motility in undiluted semen but the values obtained bore no relationship to those obtained using a haemocytometer and neither did the values obtained for laser percentage sperm with progressive motility. The mean laser velocity of the total motility was 23-64 micron/sec and for the progressive particles was 48-84 micron/sec, values which were much faster that the acceptably normal values of 8-30 micron/sec found for selected progressively motile spermatozoa timed with a stopwatch. The laser machine detected an increase in counts and the presence of residual motility after cytoplasm had been stripped away from the spermatozoa with a saponin reagent. The laser machine was unable to detect any increase in speed on increasing the temperature to 37 degrees C. It was concluded that the Lazymot machine as presently designed is not useful in the andrological laboratory for routine counting and motility determinations, mainly due to the absence of a size discriminator against the multitude of small particles that are present in human semen.

Growth fractions and estrogen receptors in human breast cancers as determined in situ with monoclonal antibodies

The growth fraction (GF) and estrogen receptor (ER) status of 76 cases of breast cancer were investigated on frozen sections of the same tissue block by immunostaining with monoclonal antibodies (Ki-67 and anti ER antibody). In 55 cases of this series, the ER status was also determined by standard biochemical methods. Our study revealed an inverse correlation between GF and ER status. This negative relationship was most significant when both variables were determined immunohistologically in the same tissue block and less significant when GF was analyzed by immunohistology and ER status by biochemical methods. These data suggest that the immunohistologically assessed ER values characterize the receptor status of a given carcinoma better than the biochemical values, which leads to the conclusion that the immunohistologically determined close negative relationship between GF and ER reflects the actual in vivo situation of a given breast carcinoma case. However, the immunohistologic analysis also revealed that there is a proportion of exceptional cases, ie, those with a positive ER status and a large or moderately large GF. Because only half of the ER-positive breast carcinomas respond to endocrine therapy with objective remission., it is hypothesized that it might be preferentially these mentioned exceptional cases that fail to positively respond to endocrine treatment protocols.

The diagnostic value of plasma free testosterone in non-tumorous and tumorous hyperandrogenism

The clinical significance of total and free testosterone (T) estimates for the diagnostic approach to hirsute patients was assessed. Plasma T was measured by radioimmunoassay and its non-protein-bound fraction was determined by equilibrium dialysis, thus facilitating the calculation of apparent free T (AFT). The cases of 162 subjects were investigated; the subjects included 75 women in whom glandular androgen release had been defined by selective catheterization. A positive linear correlation was observed between both parameters over a wide range of concentrations (T, 153 to 10,700 pg/ml; AFT, 0.8 to 342 pg/ml; P less than 0.001). Significant differences of mean T and AFT levels were found between healthy control subjects (n = 8) and subjects with non-tumorous hyperandrogenism (n = 60; P less than 0.005). Individual values overlapped considerably; elevated T (greater than 640 pg/ml; 48%) or AFT (greater than 7.2 pg/ml; 52%) were present in only half the hirsute women. However, the upper 95% confidence limits of normal for both indices were exceeded in all patients with androgen-secreting ovarian tumors (n = 7). It is concluded that the indirect estimation of AFT in addition to T is time-consuming, costly, without practical value in selecting the proper treatment, and therefore not mandatory in the routine evaluation of androgenized women.

Assessment of spermicides by a stripping technique against human spermatozoa

Fifty-two (52) compounds were tested for spermicidal activity by titration against human spermatozoa. The gradual decrease in mean sperm size was measured against increasing concentration of spermicide and the end-point was taken as the point at which all the peripheral cytoplasm had been removed and only the sperm core of nucleus and tail fibres remained. There were 14 compounds that produced this total effect. All were detergents, of various types, and the effect was purely physical. The most potent compounds caused complete stripping at 0.5-50 pmol/cell and most are already used in spermicidal preparations. A further 11 compounds, including sodium hypochlorite and some phenols, caused partial stripping, while 4 compounds caused sperm swelling. The test was not suitable for assessment of metabolic cell poisons.

The splitting of sperm heads from tails in eight mammalian species and the measurement of their sizes

Ejaculated spermatozoa from man, the Euopean wild boar and the bull, and spermatozoa from the cauda epididymes of the rabbit, rat, mouse, hamster and Guinea pig were treated with a sonic bath, a sonic probe, trypsin with and without prior treatment with a sulphhydryl reagent, pronase and alkalis. The fragments produced were counted and sized in an accurately calibrated Coulter Counter, Model ZB Industrial, before and after Zaponin treatment to lyse accompanying debris and the peripheral cytoplasm. Head and tail fractions were separated on sucrose gradients. Each species required different conditions for cleavage or fragmentation. Rabbit and bull spermatozoa were cleaved by the ultrasonic bath exactly into heads and tails, producing twice the number of particles with two peaks in the size distribution curves butith some 60% loss of total sperm volume which became the soluble fraction. The ultrasonic probe, and for the bull, pronase, produced the same cleavage but these more drastic treatments dissolved a considerable portion of the tail fraction. Rodent spermatozoa, especially the rat, were cleaved perfectly into heads and tails by mild trypsin treatment. All the nonrodent spermatozoa were resistent to trypsin cleavage, although prior treatment with a sulphhydryl reagent caused swelling and subsequent trypsin action caused digestion into miscellaneous pieces. Spermatozoa from the boar and from man could not be cleaved by any of the procedures. The sonic probe produced fragmentation with progressive dissolution of the tail fragments and a single peak in the size distribution curve corresponding to small stripped heads. The soluble fraction always constituted a large proportion of the original whole spermatozoa.

Comparison of the particle size distribution curves determined manually and automatically in an accurately calibrated Coulter Counter

An accurately calibrated Coulter Counter, Model ZB Industrial, was used to compare the size distribution curves of seven different standard particles obtained by calculation and after the attachment of a Channelyser, Model C-1000 coupled to an XY recorder. Comparisons were made at the modes of the curves and it was found that the automatic method consistently reported the particles to be slightly larger.

The interconversion of machine settings and size determinations between seven models of Coulter counter as illustrated by values for human spermatozoa

Calibration of the Coulter counter Models ZB Industrial, B Industrial D and D Industrial using 21 standard particles is reported using the same method as previously described for the Models B Medical, F and A. All the machines showed significant differences in design and sensitivity. The additional data allowed the relationship between the machine constant and the aperture diameter to be calculated and volume factors were calculated for each combination of settings on each machine. The general method of interconverting size data and machine settings between the instruments was demonstrated using human spermatozoa as an example.