Resistance of developing honeybee larvae during chronic exposure to dietary nicotine.

The effects of pesticides on honeybee larvae are less understood than for adult bees, even though larvae are chronically exposed to pesticide residues that accumulate in comb and food stores in the hive. We investigated how exposure to a plant alkaloid, nicotine, affects survival, growth and body composition of honeybee larvae. Larvae of Apis mellifera scutellata were reared in vitro and fed throughout development on standard diets with nicotine included at concentrations from 0 to 1000µg/100g diet. Overall mortality across all nicotine treatments was low, averaging 9.8% at the prepupal stage and 18.1% at the white-eyed pupal stage, but survival was significantly reduced by nicotine. The mass of prepupae and white-eyed pupae was not affected by nicotine. In terms of body composition, nicotine affected water content but did not influence either protein or lipid stores of white-eyed pupae. We attribute the absence of consistent negative effects of dietary nicotine to detoxification mechanisms in developing honeybees, which enable them to resist both natural and synthetic xenobiotics.

Novel non-sense GCH1 mutation in a South African family diagnosed with dopa-responsive dystonia.

BACKGROUND: Dopa-responsive dystonia (DRD), a movement disorder characterized by onset in early childhood and a dramatic response to low doses of levodopa, has been shown to be caused by a number of different mutations in the GCH1 gene. METHODS: We identified a South African family which presented with DRD in three family members. Polymerase chain reaction (PCR) primers were designed to span all six exons of GCH1 and the PCR products were screened for pathogenic mutations using direct sequencing. RESULTS: A novel non-sense mutation (c.233delT; p.I78fsX79) was identified in the DRD patients, which would produce a markedly truncated protein of only 78 amino acids. This mutation was also present in a number of asymptomatic family members. CONCLUSIONS: A novel non-sense mutation in the GCH1 gene can be associated with DRD and reduced penetrance in South African patients.

A South African family with the mitochondrial A1555G mutation on haplogroup L0d.

The most common mutation associated with aminoglycoside-induced deafness is A1555G and it has been found in diverse populations worldwide. In the present study we investigated a large South African family known to harbour A1555G. A total of 97 family members were genotyped using the SNaPshot technique and 76 were found to be A1555G-positive (on haplogroup L0d) and are therefore at risk of developing irreversible hearing loss. The method worked equally well on both blood (from adults) and buccal swabs (from children). Variants in the tRNA(Ser(UCN)), A10S in TRMU and 35delG in GJB2 genes were shown not to act as genetic modifiers in this family. It is important to identify mutation-positive individuals and inform them of their increased risk of developing aminoglycoside-induced deafness especially in a setting like South Africa where these drugs are still commonly used because of their efficacy and cost-effectiveness as a treatment for resistant forms of tuberculosis.

Influence of pollen quality on ovarian development in honeybee workers (Apis mellifera scutellata).

Protein-rich diets are known to promote ovarian and egg development in workers of the honeybee, Apis mellifera, even in the presence of a queen. Since the main source of protein for honeybees is pollen, its quality and digestibility might be important dietary factors determining reproductive capacity. We have compared the effect of two types of pollen-sunflower, Helianthus annuus, and aloe, Aloe greatheadii var davyana-on ovarian development in A. mellifera scutellata workers. Under queenright conditions in the field, worker bees exhibited greater ovarian development when feeding on aloe pollen than on sunflower pollen. In their midgut, we observed higher extraction efficiency for aloe (80%) than for sunflower (69%) pollen. This may be attributed to the morphology and size of the two kinds of pollen grains and explains, together with the high protein content of aloe pollen (32% dry mass in bee-collected pollen) compared to sunflower pollen (15%), why aloe pollen promoted higher ovarian development. However, in the laboratory workers sustained on aloe pollen had significantly less-developed ovaries and higher mortality than those fed sunflower pollen. These detrimental effects may be due to an unbalanced protein:carbohydrate ratio. We discuss the effects of unbalanced diets on the physiology and ecology of honeybee reproduction.

Digestion of maize and sunflower pollen by the spotted maize beetle Astylus atromaculatus (Melyridae): is there a role for osmotic shock?

We investigated the mechanism and efficiency of digestion of two types of pollen, maize, Zea mays, and sunflower, Helianthus annuus, by the spotted maize beetle, Astylus atromaculatus (Melyridae). We found similar and high extraction efficiencies, but different mechanisms of digestion. Osmotic shock was apparently involved in digestion of the large and thin-walled maize pollen grains. In the anterior midgut most maize pollen grains were already ruptured, in contrast with the intact exines of sunflower pollen, which suggests another mechanism of digestion for the latter, such as enzymatic action. We investigated the effect of osmotic shock on maize pollen in vitro by looking at the behavior of pollen grains in varying osmotic concentrations. Maize pollen grains burst in both distilled water and sugar solutions of various concentrations, and the amount of rupturing decreased with an increase in sugar concentration. Digestion of maize pollen was much slower in honeybees than in spotted maize beetles. Maize pollen bursts early in the midgut of maize beetles, but remains intact in honeybees: this suggests that osmotic shock may not be as important for honeybees as previously suggested.

The glycosaminoglycans of the gubernaculum during testicular descent in the fetus.

Tissues were obtained from 387 male pig fetuses ranging from 60 to 120 days of gestation. The relative wet mass and water content of the gubernaculum increased during and decreased after the period of testicular descent. The extracellular glycosaminoglycans (GAG) were assayed to determine whether these polyanionic macromolecules are responsible for the increased water content of the gubernaculum. The total GAG/wet tissue mass in the gubernaculum decreased during and increased after descent, while the total GAG/dry mass decreased during and after descent, indicating an accumulation of water during descent, with a loss of water and an increase in less hydrated tissue components after descent. The major GAG fraction in the gubernaculum was dermatan sulfate, but the percentage hyaluronate in the gubernaculum was two times higher than in striated muscle or umbilical cord, indicating that this GAG fraction may be responsible for the increased water content of the gubernaculum, which probably serves to dilate the inguinal canal and scrotum, thus facilitating descent.

The collagen content of the gubernaculum during testicular descent in the pig fetus.

Contracture of collagen fibres in the gubernaculum has been suggested as a mechanism responsible for fetal descent of the testis. We measured the collagen content of the gubernaculum, fetal thigh muscle and umbilical cord tissue by assaying its hydroxyproline and protein content in 194 male pig fetuses between 60 and 109 days of gestation. During the period of testicular descent (80-90 days of gestation), a decrease occurred in the hydroxyproline/wet mass and protein/wet mass of the gubernaculum, but not of fetal striated muscle or umbilical cord tissue, reflecting an increase in the water content of the gubernaculum during this period. An increase occurred in the hydroxyproline/protein concentration of the gubernaculum and fetal striated muscle, but not of umbilical cord tissue, denoting an accumulation of collagen in the gubernaculum after descent of the testis. In view of the absence of a firm distal attachment of the gubernaculum in the pig fetus, the increase in its collagen content is probably not a cause of descent by exerting traction on the testis, but merely reflects the involution of the gubernaculum noted after descent.

Hyperplasia and hypertrophy of the gubernaculum during testicular descent in the fetus.

The role of the gubernaculum during testicular descent was investigated in 115 male pig fetuses ranging from 68 to 109 days of gestation. Descent of the testis through the inguinal canal occurred between 77 and 94 days. There was a marked increase in the total and relative wet mass as well as the wet/dry mass ratio of the gubernaculum, denoting an increase in the water content of this structure during descent of the testis. Similar changes were not seen in other fetal tissues. Asymmetrical descent of the testes occurred in seven of the 40 fetuses between 81 and 92 days of gestation. Descended testes had gubernacula with a greater relative wet mass than the gubernacula of undescended testes. These findings indicate that the increase in mass of the gubernaculum plays an important part in testicular descent. An increase in both the DNA content (hyperplasia) and the RNA/DNA ratio (hypertrophy) was noted in the gubernaculum during descent of the testis. Hyperplasia in the gubernaculum occurred at a rapid rate initially and ceased after the completion of descent. Hyperplasia was also seen in the testis and epididymis, but occurred at a slower rate initially, with a rapid acceleration after the completion of descent. Cellular hypertrophy was not noted in the testis and epididymis, but did occur in umbilical cord tissue. If gonadotropins acting via androgen secretion by the testis provide the stimulus for these changes, the observed difference in response between the gubernaculum and testis could be due to a difference in end-organ sensitivity. However, it is also possible that some unidentified non-androgenic gubernaculotropin, possibly secreted by the fetal testis, provides the stimulus for gubernacular growth.

The effect of 5 alpha-androstane-3 alpha, 17 beta-diol and 17 beta-estradiol on the adult and immature chacma baboon prostate.

We have studied the Chacma baboon prostate in an attempt to develop a primate model of benign prostatic hyperplasia. Anatomically, the baboon prostate can be divided into caudal, cranial, and prostatic urethral segments. A peri-urethral group of glands has been identified in the prostatic urethra. Following treatment with either 5 alpha-androstane-3 alpha, 17 beta-diol or 17 beta-estradiol, or the hormones in combination, the mature baboon prostate showed very little response by gravimetric or morphometric analysis. In contrast, the stimulatory effect of 5 alpha-androstane-3 alpha, 17 beta-diol on the caudal lobe of the immature baboon prostate and the prostatic urethral segment (a structure that is largely fibromuscular) was potentiated by the addition of 17 beta-estradiol. The weight of the immature baboon cranial prostate was increased by 5 alpha-androstane-3 alpha, 17 beta-diol treatment, but 17 beta estradiol did not potentiate androgen-induced growth. By morphometric analysis it could be shown that both the epithelial and stromal component of the immature baboon caudal prostate responded to 5 alpha-androstane-3 alpha, 17 beta-diol (androstanediol) treatment and that the addition of 17 beta-estradiol had a slight, but significant, potentiating effect on the androstanediol-induced increase of epithelial volume.

Fluctuations in prostatic glycosaminoglycans during fetal and pubertal growth.

Mesenchymal glycosaminoglycans have been shown to fluctuate during the development of various organs. Prostatic development is an interesting example of organogenesis as it is only at puberty, under androgen influence, that differentiation is completed. We have extracted and quantitated the glycosaminoglycans of human prostates obtained from fetuses, prepubertal, and adult males to determine the changes that occur during prostatic differentiation. The total glycosaminoglycan content per prostate followed the wet weight growth curve. The percentages of heparan sulfate and heparan sulfate sulfation seemed to correlate with prostatic epithelial differentiation. After 25 years of age prostatic glycosaminoglycan concentrations tend toward the glycosaminoglycan ratios typical of benign prostatic hyperplasia.

Glycosaminoglycans of human prostatic cancer.

The glycosaminoglycans of normal, benign hyperplastic and cancerous prostate were studied. In both prostatic hyperplasia and cancer the chondroitin sulfate:dermatan sulfate ratio was increased. In prostatic cancer this increase correlated with both the differentiation and extent of cancer in the prostate. The percentages heparan sulfate and heparan sulfate sulfation were decreased in prostatic cancer. Hyaluronic acid increased with dedifferentiation of the cancer. Histochemically, sulfated glycosaminoglycans were concentrated in the prostatic stroma at the stromal-epithelial interface. The increased chondroitin sulfate:dermatan sulfate ratio may be a nonspecific response or requirement for epithelial growth.